Motive Decay

""And when he tried to steal our sunlight, he crossed that line between everyday villainy and cartoonish super-villainy.""

- Waylon Smithers on Montgomery Burns, The Simpsons, "Who Shot Mr. Burns?"

A sort of Character Derailment where a character with an initially complex and even reasonable motive for his actions is Flanderized into a Flat Character who simply does what is expected, regardless of their original motivation.

This is often someone who starts out with a specific goal, as a Well-Intentioned Extremist or someone out for revenge against the perpetrators of a particular (perceived) wrong, or someone who is driven to actions by unfortunate circumstances. This can make a very deep and often tragic characters, but it's hard for the writers to keep it up, especially in a long-running franchise, where later writers often just don't "get" it. Sometimes the writer is trying to give some kind of Aesop that because their original motive was grey, this leads to monochrome quickly. Too quickly.

This often happens when a story has several antagonists, one of whom is only needed for conflict. Expect the character to become a cartoonishly evil megalomaniac. If this happens to a side character, it is often followed by Flanderisation. Perhaps even more strangely, the other characters won't notice such decay and will, at the least, be unsurprised that this character is now a walking cliche. If this happens to a series protagonist, expect a Dork Age, gnashing of teeth and shrieks of Ruined FOREVER!

This is, if anything, even more common in stories told out of order, as a writer wishing to give a two-dimensional characters more depth will go back and write a backstory exploring the reasons behind his good or bad actions, especially as the character tends to be the protagonist of the backstory.

Comics do this a to a certain degree, as various writers are more or less interested in character depth.

As villain motivation isn't always seen as integral to the plot, expect villain examples. Compare The Dark Side Will Make You Forget, where the changing of motives is a form of Character Development. Similarly, It Gets Easier, and He Who Fights Monsters are in-story development of motives. Likewise, this may be purposely invoked in order to create a Self-Disposing Villain.

A form of Character Derailment.

Compare with: Villain Decay, Plot Tumor, Flanderisation (which is a derailing of how the character acts, not his reasons).

Not to be confused with: Out-of-Character Moment, Unbuilt Trope and Character Development

Anime and Manga

 * Magical Project S Pixy Misa starts every episode ruining the balance of good vs evil (that's her purpose) but ends acting for the Evulz and more often than not ends vacationing (justified in that she is not actually evil but she just represents the repressed aspects of Misao and doesn't really care for her goals) instead of torturing Sammy and even in one episode she ended having literal vacations instead of destroying Sammy.
 * Pokémon: Brock's life goal was to be a great Pokémon breeder. You'd never know it nowadays. He finally left the show becoming a Pokémon doctor.
 * Misty wanted Ash to repay/replace the bike he inadvertently trashed in the first episode, which is why she followed him around so much. Near the end of the first season, we find out that she actually forgot about the bike, and begins hounding Ash about it when he accidently reminds her. before she left the show for May.
 * That nearly-forgotten motive's referenced in the DVD commentary for the English version of the first movie. The director relates that, while they were trying to come up with an appropriate two-syllable translation for Misty's horrified reaction to Ash's apparent death, Misty's voice actress Rachel Lillis ad-libbed "my bike!"
 * Also, Ash's goal was To Be a Master; that is, to become the world's greatest Pokémon Master (a Pokémon Master being a trainer who is an official part of the Pokémon League). Nowadays, this goal is barely referenced, and Ash seems to be going around fighting Pokémon battles for the heck of it. In Season 9, he was even offered the position of Frontier Brain, which would make him a Pokémon Master, but he turned it down.
 * We actually don't know if it would have made him a master. The definition has never been clearly defined.
 * His goal seems to be to be the grand champion of a major region (Orange Islands doesn't count, apparently). Then again, Ash seems more interested in the journey than the destination; he takes no shortcuts getting there and prefers to just travel the land instead of settling into some position of power. It's likely that "To Be a Master" was just an excuse from the start.
 * The Team Rocket trio, who originally decided to follow Ash because his Pikachu blew up a Pokémon Center. Since they were trying to steal strong Pokémon, this made sense. Through the show's run, however, we have encountered numerous Pokémon who are significantly more powerful than Pikachu. They continue (on and off) to attempt to get Pikachu because they refuse to give up, even though their boss never cared about Pikachu in the first place.
 * Ralph in Soukou no Strain went from military golden boy to psychotic traitor The trauma drove him insane, which may explain why his motives go from Set Right What Once Went Wrong to Kill All Humans.
 * This sort of thing happened across international lines as part of 4Kids! Entertainment's dub of Yu-Gi-Oh!. They usually played down the sympathy-inducing backstories of the villains and made them more evil. Pegasus' goal was the same (to bring back his lover Cecilia) but the methods were more ruthless. In the original, he needed to defeat Yugi so that he could gain control of Kaibacorp's technology and create a hologram of Cecilia to live with. In the dub, he wanted Yugi's Millennium Puzzle and all Millennium Items so that he could bring Cecilia's soul back and infuse it into the hologram. It's said in the dub that in doing so, he could inadvertently destroy the world. Although probably unintentional, this motive shift actually makes sense in the long run, as the seven items together DO open the door to the afterlife (where Pegasus could get Cecilia's soul) and also unleash the power of Zorc Necrophades into the world, which could indeed destroy it against Pegasus's wishes (this is Yami Bakura's intentional goal.)
 * Marik/Malik got it worse, though. In the original, he simply wanted to escape the life of a tomb keeper, kill Yugi (more specifically, the pharaoh), whom he believed had killed his father, and live peacefully ever after with his sister and stepbrother. In the dub, this is changed to him wanting Yugi's Millennium Puzzle and the God Cards to rule the world "as pharaoh". It's even worse with Yami Marik, who, in the original, was essentially the Joker with ancient Egyptian shadow magic. In the dub, he wants to rule the world, too.
 * Meanwhile dark Bakura suffered this in-universe for a while, retroactively. He turns out to have had fairly good reasons for messing with the royal family, at one point, which somehow became a plan to destroy either Egypt or the world, partly because the spirit of hatred born from the slaughterof his family (Japanese) or an ancient primal destructive dark thing (English) teamed up with him. He seems to have entered the series with amnesia, carrying him still farther from sanity. But he gets back to the revenge-and-end-of-world thing in the Millenium World arc.
 * Divine of Yu-Gi-Oh! 5D's starts out as some sort of Visionary Villain, being the leader of a movement giving shelter to the repudiated Psychic Duelists, wanting to form an army with them to take revenge on all the people hating and shunning them, making the world a better place for Psychic Duelists. Though his plans got foiled by his sudden death. But miraculously he returned and Character Derailment did take the best of him. While he was always close to the Moral Event Horizon, but also had his goals and clearly shared more with Aki than just mind control, he suddenly forgot all about his earlier intentions, turned into a psychopathic dumbass, causing his own death with the most ridiculous Engineered Public Confession and got eaten by a giant frog just in time to exculpate Aki from all guilt and before he was about to kill the main character.
 * Divine is subject to a bit of Alternate Character Interpretation, on account of the fact that he's such a Manipulative Bastard that it's hard to discern where his facade of geniality ends and his actual feelings begin. Does he truly care for Aki on some level, or is he just using false kindness to make her more and more emotionally dependent on him? Is his goal really to demand societal acceptance of psychic duelists and take revenge on those who shunned them, or is he just raising a personal army of Tykebombs to do his bidding? Is he merely ruthless in pursuit of his goals, or is he an outright sociopath? Depending on how the individual viewer answers these questions, it's arguable that his in his reappearance after, he hasn't undergone Motive Decay but has simply dropped all pretenses.
 * Must have been a lot of pretense and especially braincells to drop if he was intelligent enough to hide all those evil motives and sociopathy during the first one and a half arc, but all of a sudden completely forgot better not to insult the owner of a Jibakushin, which was in the near vicinity to boot.
 * Naraku in Inuyasha has changed motives so many times that eventually he was evil just for the sake of being evil. Initially, he was driven by his lust for Kikyo and hatred for Inuyasha, both stemming from his time as a human. Once he got over that, he wanted to use the Shikon-no-Tama to purge his human self and be a full-fledged youkai. And once he did that without the jewel, he was pretty much evil for the sake of evil. The jewel is supposed to grant wishes, and when Naraku finally gets the jewel, he decides not to wish on it, but just to use it to kill Inuyasha. Naraku himself says he's not sure what comes next when he's done that. Yes, that's right - he spends over 500 issues of the manga trying to get the jewel, and once he finally has it, he's not sure what to do with it.
 * Doubly justified. For one thing, Naraku is a sort of collective entity that spends much of its time attempting (and succeeding) at absorbing other Youkai into itself, so it is reasonable to expect his personality and goals to change to a significant degree (it has even been a plot point on occasion). On the other hand, from the start Naraku has been established as basically the distilled evil of a multitude of Youkai, which just happens to have a little connection to a deceased human. He carried some memories and drives from that human for a time, but got over them eventually.
 * This trope was actually lampshaded when Naraku basically separated his human heart (and thus Onigumo) from his body. Onigumo angrily complained that after selling his soul to the demons, nothing went the way he had expected.
 * Orochimaru's experiments in Naruto and his usage of different bodies form ninja, started as a method to learn every jutsu and gain immortality. However, his continuous experiments in the Cursed Seal seem not to do that and turn them into monstrous beings, not really related to his original goal. Sasuke actually called him out on this before finishing him.
 * Inverted with Sasuke. His goals have always remained more or less the same: kill his brother, Itachi, and restore his clan, but how he plans to accomplish these goals has begun to vary wildly as the deterioration of Sasuke's mental state has become more rapid. After Itachi's death, his goals switched from killing Konoha's elders, to killing Danzo, to destroying Konoha, to killing every last man, woman and child in Konoha because he believes they're laughing at him over the totally unprovoked destruction of his clan.
 * Tobi is arguably a case of this as well, though it's possible it'll be averted if the author decides to explore his motives more. It's helped by the fact that The Reveal
 * With Kabuto people aren't even sure if he has a real motive for working with Tobi or what his future plans are at all. It's all Epileptic Trees with him right now.
 * Recent chapters showed Kabuto as suffering from a lack of identity stemming in part from his orphan status, and wishing to acquire an "identity" for himself through means similar to Orochimaru's immortality hunt: get every jutsu possible.
 * Jerid Messa from Zeta Gundam starts off as an ambitious elite soldier (by mediocre Federation standards), and has the goal of one day leading the Titans forces, even if the only reason is for the power that such a position would provide. A number of situations in the series even make him a relatively good guy in everyday life. After one too many fights with the series protagonist, he has transformed into an individual completely focused on nothing but pure bloody vengeance.
 * To be fair, his breakdown is largely precipitated by the death of his love interest Maua Pharaoh. Who was one of the more decent characters in the series. While she's on the "bad guys'" side, she's never shown to do anything morally reprehensible herself, which is saying something in a series where even a good number of the "good guys" former nazi-expys with questionable motives and war crimes on their rap sheets.
 * Same for Mashimar Cero in Gundam ZZ. Captain of a Neo Zeon ship, very idealistic and unwilling to authorize actions that would endanger civilians. Tries to keep his cool and conduct battles in a way that would make Haman Karn proud of him. Ducks out early on after it's decided he's not up to the task of defeating the hero... only to come back later on as a cold and merciless soldier. In an aversion though, if final battle still shows him as the lesser of two evils due to an Enemy Civil War, and he gets to go out in a blaze of glory.
 * This is a side effect of having even more Cyber Newtype enhancements. Best case scenario, the enhanced person goes a little nutty. Worse case scenario, they become raving lunatics hell-bent on causing as much property damage as possible. Mashimar tends toward the latter.
 * Blue Cosmos from Gundam Seed suffers greatly from this trope. Originally they were an environmental pressure group, but after Human genetic enhancement became possible they shifted their focus to preventing widespread genetic modification. After genetic enhancement did become widespread they became a militant/terrorist organization bent on killing anyone who had their DNA altered. When war finally breaks out between the genetically enhanced Coordinators and the natural humans of Earth Blue Cosmos begins artificially enhancing their own people to fight one on one with the Coordinators. Then it all turns out they were just a catspaw to Logos who do it for profit.
 * Suzaku Kururugi in Code Geass starts off as a heroic upstanding fellow, who wants to change the system from the inside. After the, he more or less seems to go temporarily insane, leading to a justified battle with the Magnificent Bastard Protagonist Lelouch. However, in the interim between both seasons going well into R2, not only has he become a Jerkass of ridiculous proportions, he has sold out his old best friend for a step up the power ladder, and his goal of changing the system from within has degraded to making his own homeland a better place (effectively giving the rest of the enslaved Areas of Britannia the middle finger).
 * The Black Knights undergo a similar one in R2 19 when they in exchange for Japan, at the expense the rest of the world represented by UFN, for which the B Ks made up the primary military force, and their fight against Britannia's dominion of the world, not to mention that there was no actual guarantee that Britannia would keep their hands off of Japan once and for all. (And of course their own ally Kallen was nearly caught in the crossfire.) None of this went very far at all, given that Lelouch was whisked away by Rolo in a  the moment things started to go south, and Xingke and Kaguya would soon catch Ohgi trying to cover the whole thing up.
 * After the aforementioned event in addition to, Lelouch, who prior to the betrayal had actually assembled a legitimate front in the UFN to battle Britannia, now decides to go it alone, abandoning all personal inhibitions and willing to use his geass on anyone and go to even more drastic extremes, including making Faceless Goons Slave Mooks out of his new army, detonating the world's biggest energy reserve and apparently causing more death and destruction than he did during his rebellion pre-betrayal. The latter (or former technically) was at least somewhat justified because of the opposition he faced off against. It's not that he became evil per se; the plot justifies it as . However, given the leading circumstances and the plausibility of such a plan (and even Lelouch's own admission that it was a gamble), it all seemed like a convenient death wish for him. Not to mention that the aforementioned fact that causing worse, unnecessitated destruction was a path to atonement, even as a mask, when it is even noted in side materials by Lelouch that there are other methods, makes it seem more a case of Designated Evil than Necessarily Evil.
 * Charles being a Well-Intentioned Extremist reveals him to be worse than Lelouch and Suzaku combined in this regard. He conquered most of the world.
 * Asuham Boone in Overman King Gainer wants revenge on Gain for his sister, but is an overall good guy. Eventually his obsession as Gain continues leading the Yapan people to Yapan leads him to decide to freeze the world using the Overdevil. Its eventually revealed that Asuham's sister had a one night stand and Asuham overreacted.
 * Roy Mustang starts out trying to become the best damn leader in the world, but it starts to go wrong when he faces Envy, . Fortunately, Hawkeye helps him out.
 * Haru, The Hero of Rave Master, had a pretty easy motive "I want to save the world". He keeps it up for all 35 volumes. It's the Big Bad, Lucia, who can't seem to decide what his reason for fighting is (lampshaded once). When he first appears he claims to simply be after power, then he wants to prove his family isn't crazy (by taking over the world), then he wants to be a god, then he wants power again, then he wants to break some curse that was put on his family for stopping humans from going extinct by making them all die after all.
 * Toward the end of Speed Grapher, someone with the people skills and political savvy to become Prime Minister becomes an all-consuming openly megalomaniacal beast with nothing more important to do than indulge in evil laughter and pull grotesque faces. What makes this Egregious is that before he appeared to have a plan with substantially evil implications on the lives of real people, but that all degenerates into Bond Villain Stupidity just to terrorize a little girl he claims to worship.
 * Far in the backstory of Full Metal Panic, Amalgam was founded with good intentions. They actually played a key role in the defusing of the Cuban Missile Crisis. Unfortunately, they were founded shortly after WWII and the main story takes place in the 90s. In the roughly 50 years between its founding and the main story, virtually all of its members had retired and been replaced by people who had different goals and used the organization to achieve those goals instead of the ones set forth by its founders.
 * Over the course of Death Note, Light Yagami's megalomania causes him to completely lose sight of his original goal (to improve the world by removing its criminal element) and degrade into using the Death Note to destroy his enemies. Many a character points out that he's little better than a serial killer by the end, but Light's so blinded by his pride that it takes for him to catch on.

Comic Books

 * Recurring Teen Titans character Deathstroke the Terminator a.k.a. Slade Wilson started out as a ruthless, though not unscrupulous assassin who honestly didn't have any great animosity towards the team and originally only came into conflict with them as part of fulfilling a contract that his son died trying to complete. When he dropped the contract he actually became rather amiable towards his former targets and actually counseled grief stricken members of the team on occasion and teaming up with them fairly regularly. While his relationship with the team eventually went sour again, it really doesn't explain him suddenly becoming a Card-Carrying Villain and doing things like injecting his only surviving child with a Psycho Serum and implanting a chunk of radioactive kryptonite in her eye socket and nuking Bludhaven to spite Nightwing (a character he had previously had a lot of respect for). When pressed for a reason why he'd become such a monster his only answer was because he blamed Nightwing and the Titans for all the loss he's experienced in life, namely his children dying/abandoning him, despite the fact that it had been established that his sons had died under circumstances out of both the Titans' (and Slade's) control and his daughter abandoning him was unquestionably his fault. Since then, Deathstroke has basically engaged in nothing but wanton villainy, leaving him basically devoid of any of the complexity of his original characterization.
 * Perhaps not so coincidentally, Deathstroke's shift into a Card-Carrying Villain happened around the timeframe the Teen Titans animated series debuted, wherein Slade's character was more-or-less a Card-Carrying Villain from the start and likely contributed (albeit negatively) to the characterization of his original comic book counterpart.
 * Magneto, of X-Men fame, has cycled over the years between a Well-Intentioned Extremist and a simple Evil Overlord according to the preferences of his writers.
 * In an issue of Spider-Girl, there's reports that Magneto's been spotted (despite disappearing some time ago), and everyone's on high alert, with the X-People, Avengers, and Fantastic Four on the lookout, cautioning anyone to call in back-up if they see him. When Spider-Girl and a young X-Person spot what looks like Magneto, they quickly come to the conclusion that it's just someone posing as the powerful mutant because, come on, would Magneto really be robbing a bank?
 * Similarly, in Spider-Man, Doc Ock bobbed up and down from wanting to complete his life's work, world domination, petty thievery, and just wanting revenge on Spidey for past humiliation. Usually excused by the fact that the accident made him plumb crazy, and of course the AI in his arms was screwing with him.
 * Don't forget his short foray into trying to cure AIDS!
 * In all fairness, in-universe it was believed that he was trying to create some form of biological weapon. Only the readers knew that he was searching for a cure purely to save
 * There was one comic where Ock had a rival who'd stolen his design for the arms. There was a three-way between Ock, Spidey, and the rival in a hotel, and when the rival took out some support columns Spidey tried to get people out. Ock braced the falling ceiling and got people out - but then let it fall on Spidey.
 * In a rare positive version of this trope, Lex Luthor, Superman's Arch Enemy, started out wanting revenge on the Man of Steel for making him bald (yes, really. Of course this happened in the Silver Age, when goofy motivations abounded...) even though it was also because Superman accidently destroyed his lab as well as the lifeform he created which Luthor attributed to jealousy. Nobody complained much when this motive decayed away, even though none of its replacement motives for being Superman's nemesis are as clear-cut. Lex himself would tell you that he's doing it to prove to humanity that they don't need an alien savior and that when Superman is gone and humanity rules itself again (with Lex, as the smartest and best human, naturally in charge), he'll use his genius to cure cancer and rescue kitties and make the world wonderful. Superman would counter that by pointing out that he was gone, for a year (and until he came back, it seemed like he'd be gone forever), and Lex spent the year... plotting ways to kill Superman.
 * Of course, if someone ever points that out, Lex will respond by simply claiming that Superman has "ruined" him and turned him evil. This is pretty consistent with Lex's general Never My Fault attitude.
 * Grant Morrison's All-Star Superman gives Luthor's obsession with beating the Man of Steel a simple explanation that in hindsight makes complete sense: If it wasn't for Superman, Luthor would be running the planet.
 * Another Superman villain, the Silver Banshee. Originally she came to Metropolis from Scotland to retrieve a book that was payment for her powers. Eventually she got the book, was dragged into the underworld, brought back, and promptly vanished. Now whenever she appears she causes random problems for no real reason.
 * When she guested on the Smallville episode Escape, Clark points out that the people who wronged her have been dead for over a hundred years, so her revenge is already complete, and that her killing random people doesn't accomplish anything. She answers, "Maybe, but it makes me feel a whole lot better." Then she attacks him.
 * The Spider-Man villain Venom could be said to have lame motivations from the start, wanting revenge on Spider-Man for exposing the truth about Eddie Brock's shoddy reporting when he should have arguably done a better job himself. This trope is inverted in the various screen adaptations of the Spider-comics, as both the 1990s cartoon and The Spectacular Spider-Man cartoon, as well as the Spider-Man 3 movie, all take their time to build up Peter Parker's animosity with Eddie Brock, giving him more and better reasons to hate Spider-Man than he ever had in the comics, and making their animosity more personal. In the original comics, Eddie Brock was unveiled without much buildup, but subsequent takes on the Venom character develop Eddie Brock on his own, before any contact with the symbiote.
 * In the comics, it morphs into that Eddie decides that pre-symbiote, he was innocent and Peter screwed with all that by destroying his career. Eddie decides to go off and protect innocence in all its forms, which has the side effect of making the audience like him (he doesn't intentionally kill the good guys anymore).
 * Also, it's been retconned that he real reason Brock decided to kill himself the night he bonded with the symbiote wasn't solely because Spidey ruined his career; it turns out Brock had terminal cancer, and the death of his career was just the final straw.
 * The recent Venom: Dark Origin keeps the lame motives, but brilliantly analyzes Eddie's past and shows that he is deeply mentally disturbed. And the ironic thing is, in real life, sometimes minor slights really are enough to make somebody your enemy.
 * Herr Starr from Preacher (Comic Book) is an example of this as intentional character development. At first he is a Well-Intentioned Extremist, but after a series of unfortunate events that leave him mutilated, he becomes disaffected and gives up on his quest to better the world and merely seeks revenge. He openly states, after being told that he is a monster, that "Yes, I suppose I am. I became one a long time ago. At first in order to save the world. Now merely for the sake of vengeance."
 * Ironically, this may benefit the world anyway thanks to his actions leading to the complete and total collapse of the Grail, averting their world domination scheme.
 * Darkseid of Jack Kirby fame. His motive was to find the Anti-Life Equation and enslave the universe. Forty years later he just keeps showing up to mess with Earth and the Justice League of America. He finally managed to get back on track in Final Crisis.
 * Averted at the end of Final Crisis: Legion of 3 Worlds with.
 * He returns in a Blackest Night tie-in though
 * Spider-Man Arch Enemy the Green Goblin began his career as a ruthless businessman who sought to take over the criminal underworld, having already conquered the world of business. A number of failures at the hands of Spider-Man slowly downgraded his motives into ever more personal revenge on the spider, to the point where eventually Norman Osborn's entire life revolved around Spider-Man.
 * Though recently, he kept his eye on the ball and has taken over Fury's job.
 * Although even through that, he kept up the petty obsession with Spider-Man, he just had more resources to help him bear down on it. For instance, when working through his "List" of obstacles to take care of, he saved Spider-Man for last. Not because Spidey was any great threat(at least, no more so than any other individual hero), but because he wanted to give himself a "reward" for finishing the other items on the list.
 * Several Wonder Woman villains:
 * The third Cheetah, who started out as a tomb raider greedily obsessed with mystical artifacts, hasn't mentioned them in about two decades, substituting that for just trying to kill Wonder Woman for whatever reason.
 * Giganta's motive, on her debut, was to escape her dying, pain-wracked body. She did that; since then, she's switched bodies again, and spends her time committing random criminal acts.
 * Circe, at least, started out trying to destroy Wonder Woman, but the specific reason why was resolved in 1991. Since then, exactly what she wants has been changeable and vague.
 * "Yes, my evil, nefarious, diabolical plan to... to... wait, what the hell was my plan? And what was I trying to achieve with it?"
 * This is canon and justified for the Crucible in Knights of the Old Republic. The organization was created by one of the ancient Sith Lords to capture and train slave-soldiers for his armies, but by the time of the comics he's been dead and gone for centuries and the Crucible's only purpose for its crimes now is to perpetuate itself.
 * This has really become just a general result of supervillainy. Whatever reason the character was introduced, the self-perpetuating nature of the comics medium ultimately means that in order for the villain to put in a return appearance, they need a reason for him to be acting as a villain again. Once the original motive inevitably runs dry, many writers fall into the trap of "Supervillain A wants vengeance against Superhero B for defeating him the last 31 times he tried to complete his motivation!", which will be the character's new motivation for the rest of time.
 * The most cut-and-dry example of this variation in action is the vicious cycle of Doctor Doom and Reed Richards of the Fantastic Four. Doom originally had a murderous grudge against Reed because he blamed him for a botched experiment that scarred Doom's face, injured his pride, and got him expelled. However, every time he's tried to kill Reed or Take Over the World in order to get the power necessary to kill him, Reed manages to beat him, hurting Doom's pride even more because it proves Reed is still smarter than Doom, which makes him hate Reed even more, which causes him to redouble his efforts to kill Reed, which cause him to get defeated by Reed again, which hurts his already-injured pride even more, which makes him hate Reed even more... ad infinitum.
 * Pretty much all Doom's Evil Plans suffer from this: no matter how coldly calculated and self-serving his manipulations are, and no matter how hard he tries to convince himself that he's doing it just to Take Over the World, they all eventually derail into an attempt to destroy Reed Richards' life.
 * Marvel villain The Hood originally had some sympathetic motives for becoming a supervillain, such as supporting his family. He gradually began to love the power his new hood and boots granted him more than he loved them. When he lost the hood and boots that allowed him to channel the power of Dormammu, he leaped at Loki's offer to repower him with the Nornstones. When he lost those powers almost as soon as he got them, he didn't take it very well. Then he went after the Infinity Gems. He seems to be addicted to power for its own sake.
 * The major point of contention with fans of the Archie Comics Sonic the Hedgehog series and Ian's interpretation of the Dark Legion; before he took over, they were written as Well Intentioned Extremists focused only on undoing a Straw Political-based technology ban and be reintegrated into main Echidna society without having to sacrifice their Machine Worship lifestyle, and have at several points sided with the other Echidnas against shared threats. After Ian took over? They got Flanderized into generic Mecha-Mooks who force-cybertize other people into their ranks.
 * Subverted by the Shocker, a charter member of Spider-Man's Rogues Gallery. All he really wants is to make a dishonest buck, and he otherwise doesn't really care about Spider-Man. The problem is that keeps running into Spider-Man over and over and over again every time he tries to commit a robbery or a hired killing...
 * Another subversion comes from the Beetle, an enemy of Spider-Man and the Human Torch. While he first sets out to get revenge on both of them, his defeats made the Beetle realize that revenge was a sucker's game and he resolved to only stick to straight crime. When the Kingpin's Arranger tried to hire him to kill Spidey, the Beetle flat-out refused...but the Arranger set up a situation where the Beetle ended up fighting Spidey anyway.
 * Despero, Justice League foe. When he first appeared he was a weird-looking alien despot, backed up by unseen tech that could teleport people and subdue them, fighting the heroes because they had accepted some refugees trying to overthrow him. But the more he gets used, the more power he gets and the less motive he had, so that as of just before Flashpoint he was a walking tank with telepathy, but apparently homeless and just battling the heroes because... revenge or something?

Film

 * Enchanted. Narissa not only has Giselle but Prince Edward out of the way, but instead of blocking their way back to Andalasia, insists upon Giselle's death.
 * Arguably a case of Dangerously Genre Savvy. Basically, "Why Don't Ya Just Shoot Him".
 * Norman Osborn, aka the Green Goblin, suffered from this in the first Spider-Man. At first he wants to off some jerks who are attempting to sell his company, Oscorp. The thing is, after he successfully kills them all, he inexplicably continues to commit seemingly random villainous acts, and is constantly saying things like "Spider-Man is the only one who can stop me," or "Think of what Spider-Man and I could accomplish if we joined forces!" Of course, being a nutcase will do that to you...
 * In the third, Sandman steals money to buy medical treatment for his sick daughter. He seems to forget about her completely after Spidey foils his first attempt and teams up with Venom for revenge. Instead of, for example, going to another city and/or trying again.
 * The Government in Starman. The alien's spacecraft was originally shot down under the assumption that it was a Soviet attack, but it's later definitively established that he's an extraterrestrial. NSA Chief George Fox (Richard Jaeckel) still wants to kill him because... well, who knows? Just to be evil, apparently.
 * Shinzon experiences this within the course of one movie in Star Trek Nemesis. Initially he wants to free the Remans, and so he takes over the government in order to do this. Then for some reason he decides he's going to destroy Earth and Mind Rape Troi just for the hell of it.
 * Alternately he was evil all along and freedom for the Remans was simply a ploy to get Picard to trust him.
 * The Italian Job (2003) starts out with a group of thieves making a heist and getting away with $35 million in gold. Then,
 * Justified, because they stated that they wanted revenge from the beginning.
 * Imhotep in The Mummy Trilogy films. In the first film, his every action, from betraying his liege to attempting to kill the Female Lead, stems from his undying (literally) commitment to his lover and desire to be with her. That he brings about the end of the world is incidental, the result of being Cursed with Awesome rather than a desire for mass murder or conquest. In the second film, he gains a sudden motivation to challenge the long dead Scorpion King in order to gain control of an undead army and conquer the world, this despite the fact that his love interest is alive and well, together with him, and that he already possesses substantial magical powers. The reasoning is mentioned briefly and never talked about again. The events of the first movie stripped him of his immortality forever, so he can be killed by anyone with a gun. The cultists seeking to bring him back want him to kill the Scorpion King so he can use the Army of Anubis to take over the world from a safe distance. It could be explained that since his true love was alive with him and he had immortal, supernatural powers again, they might as well rule the world together, or that while reviving her was his first priority, afterward he wanted to move on to other, less important things. Since we only have his actions and other people's word as to his motives, it's a bit unclear.
 * It could also be explained by the fact that Ankh-Su-Namun appeared to be working with cult, she wanted to rule the world, and Imhotep went along with it because it was what she wanted.
 * In Steven Spielberg's The Terminal, there is an example with Immigration Officer Frank Dixon. At first his motive is simply to get Viktor Navorski out of his terminal, but when Navorski's immigration problems are finally sorted and he is able to leave to go to New York, Dixon attempts to stop him for no adequately explained explanation.
 * Pride. In reality this kinda thing doesn't happen this way, they have rules for it, had Viktor simply violated any of the rules, or left the building, he would have been taken into custody and much more quickly had his situation handled because attention was brought to it. By "playing" Dixon's game and adapting to what new rules were being applied (making a new job so Viktor couldn't get quarter returns from carts so he could eat, getting paid under the table for construction, living in a closed terminal, a close friend violating terms of citizenship so Viktor wouldn't be in trouble) he beat Dixon's attempts to get rid of him, and so if he couldn't win, neither would Viktor.
 * Happens midway through X-Men Origins: Wolverine.
 * Magneto's characterization is particularly inconsistent in the X-Men movies: in the first one, he wants to make everyone mutants so that the world can live as brothers (admittedly, he isn't swayed by the fact that the machine will actually kill people instead). By the third movie, Magneto is killing far more mutants than humans -- mostly mutants who are willingly following him. To emphasize his shift to Skeletor evil, he not once, but twice announces that "In chess the pawns go first" as his minions die/get depowered pointlessly before him. After the minions fall, he calmly notes "That's why the pawns go first." Of course, . He wasn't a particularly nice guy earlier, but the third movie takes it much further.
 * By this point it should come as no surprise that this motive decay was a result of a change in directors.
 * Clyde Shelton of Law Abiding Citizen had a good start: a complicated Evil Plan to get sweet revenge on the men who brutally murdered his family (one of whom was free after 5 years thanks to the prosecution's bungling). Then he took his revenge further; wanting to kill every official involved in the original trial and eventually  all in some half-baked bid to up-end the justice system.
 * It's easy to miss the point of his master plan he's got going. But really, he had snapped to some extent. Once his direct revenge on the two who killed/raped his family was accomplished, his goal was to force people to face the flaws in the justice system (specifically those relating to cutting deals with the guilty and playing politics instead of pursuing justice for victims). It all comes together with his satisfied response to being turned down for a plea bargain at the end of the movie.
 * Terry in Karate Kid 3. He's supposed to be helping his friend get revenge. The problem is, his friend was really disgraced by his own actions in Karate Kid 1 encouraging his students to bully another kid and to cheat in the tournament (which is the only plausible explanation for why Kreese went bankrupt after one tournament loss) and Terry indicates he's aware of this when he pretends to be a good guy to gain Daniel's trust.
 * Anakin from Star Wars turned to The Dark Side to save his beloved wife from dying. He ended up murdering her in a fit of jealousy/paranoia.
 * Incidentally the Trope Namer for The Dark Side Will Make You Forget, but...yeah, that's a bit sloppy.
 * Inverted in the Halloween films. Michael's motives are actually fleshed out in Rob Zombie's reboot. However, it turns out the fans liked it more when Michael was a soulless, mysterious psychopath.
 * This is probably because the "motive" explained in the remake pretty much boils down to a cliché Freudian Excuse.
 * The Sense Freak Cenobites of Hellraiser start out as "explorers in the furthest reaches of experience." The Lament Configuration summons them, but the people who are drawn to solving it are really drawn to the experiences the Cenobites can provide, although most aren't prepared for the extremes they're capable of. And then...
 * In the second movie, it's suggested that the Cenobites are agents of Hell and punish people according to their vices. In the third and fourth movies, Pinhead is made more evil just for the sake of it. The church scene is a good example.
 * The fifth, seventh and eighth movies are far more psychological in nature and have Pinhead as more of a judge of those whose hedonism and/or ego has made them irredeemable. The sixth and ninth movies largely go back to the original characterization.
 * In Runaway Jury, Doyle works for the defense. He's sent to find out some information about someone on the jury. Near the climax of the movie, his boss (played by Gene Hackman) tells Doyle he needs information before the jury deliberates. Doyle blows him off and continues to investigate, which makes no sense at all. Instead of
 * The point of this is that if said juror
 * The point of this is that if said juror

Literature

 * Murtagh from The Inheritance Cycle was derailed from a sympathetic villain who works for the Big Bad in order to make the world a better place to a one-dimensional snickering cliche that rivals Snidely Whiplash. This could be considered a Take That to how he was becoming something of a Draco in Leather Pants to certain sections of the Hatedom, although of course, Your Mileage May Vary.
 * It doesn't help that Galbatorix literally made it impossible for Murtagh to convert to Eragon's side. Really, someone who physically can't choose for himself which side he fights for is going to be miles more sympathetic than someone who can choose and mindlessly calls a person evil when that person, again, literally has no choice in the matter.
 * Victor Helios in Dean Koontz's Frankenstein series first desires to eliminate humanity and replace it with a masterrace of his own creation, and eventually take over the world and the universe. In the sequel series,
 * Artemis in the book Acheron, one of the most recent books in Sherrilyn Kenyon's Dark Hunter series starts out as a friendly and curious goddess at the beginning of the book. At the end, you just want to smack her for her unadulterated meanie abilities.
 * Older Than Steam: Satan in John Milton's Paradise Lost initially views corrupting mankind as a continuation of the fight for freedom from God. When he realizes that his rebellion against God has been a terrible mistake from the start, he decides that he can no longer be good and must embrace evil as his good. Later on, his motives further degrade to something akin to "Since I'm evil now, I must cause God as much trouble as possible." This decay is likely deliberate, as the whole arc of Satan being diminished in mind (as well as stature -- from towering angel to serpent) exemplifies just how destructive evil can be to its practitioners.
 * Middle-Earth:
 * Related to the Satan example is Sauron in Tolkien's legendarium -- he starts out as a clever, manipulative Magnificent Bastard in The Silmarillion, who works with Morgoth only as part of his agenda to bring order to the world, then gradually degrades to the Kill'Em All type seen in The Lord of the Rings. This was a deliberate piece of decay on Tolkien's part, due to his belief that evil usually starts out with some kind of high-minded ideal but its methods (and Sauron's multiple deaths) eventually ruin its practitioners, leaving them arrogant, hate-filled, mindless destroyers.
 * Even more pronounced is what happened to Sauron's former boss, Morgoth (who is intended to be Satan). He started out wanting to create and be the God of his own universe. But as he realized that nobody but God could actually be omnipotent, he gradually descended into a pure Omnicidal Maniac, with a corresponding loss of his power as the mightiest angel. At least Sauron kept the same basic goal (wanting to rule the world) in mind the whole time, even if he reason shifted from "I'm the only one who can run things right," to "UNLIMITED POWER!".
 * Played straight as an arrow in the ongoing Star Wars EU Legacy of the Force book series. In the first book of the series, Jacen Solo has visions of galaxy-wide destruction, including his dueling and killing Luke, that can only be prevented by accepting the teachings of the Sith. Lumiya, a former Vader apprentice, softens the blow by teaching Jacen that through careful discipline and sacrifice, he can avoid falling into darkness like Vader and the Emperor. However, with each successive book, his altruistic motives are shown less and less, slowly replaced by ever-increasing anger, distrust, intolerance, and desire for power. All of the culminates when he, who had caught onto his downfall, for a reason (or at least a rationalization) that makes almost zero sense and was later completely abandoned by the series. In a more recent book, he Force-chokes a young lieutenant to death for a perceived error, despite the fact she followed all standard procedures and was commended earlier in the book for her attention to detail. At this point, almost all trace of his benevolent motives are gone and all that remains is the Dark Side.
 * As others have noted, Motive Decay seems to be an occupational hazard of Sith Lords. Every Sith whose motives we've had an opportunity to examine started down the "dark path" for reasons that would make sense to normal people. Some want to unite the galaxy (decent motive), or to protect loved ones (ditto). Even the worst 'merely' want personal power- which isn't an inexcusable sin in and of itself. And yet every Sith we've seen has degenerated into committing acts of sheer evil. This suggests that the trope in question is intrinsic to the Star Wars concept of The Dark Side. In the Star Wars galaxy, a Sith's motives decay themselves.
 * Heck, a common fan theory (probably the result of an accidental Expansion Pack Past in the Expanded Universe) is that even Palpatine had sympathetic motives at some point--he wants the galaxy united because he's foreseen the Yuuzhan Vong invasion. This is, of course, something of a cart-before-the-horse situation.
 * Emperor Jagang in the Sword of Truth books starts out as a man who believes in human superiority and unlimited potential, and believes that magic prevents the men from creating a technological society. Later, he is a religious fanatic/OmnicidalManiac who believes that all men are evil and unworthy of life, and it's his defeat which causes a sudden technological development. At the point of his change, the books take a strong right turn into Objectivist didacticism.
 * Reversed in the Vorkosigan Saga, where the Cetagandans were introduced as pretty generic bad guys, defined by militarism and expansionism, but were soon developed as an entire society with hints of a history, changing goals, and internal disagreements.
 * In the Heralds of Valdemar series, this explicitly happens to Big Bad Ma'ar, alongside and combined with his Villain Decay. In the Mage Wars he was a Well-Intentioned Extremist who united the barbarian tribes and sought to impose a Utopia Justifies the Means. Through successive reincarnations and overuse of Blood Magic, he eventually devolves into a twisted, megalomaniacal schemer whose grandiose plans to Take Over the World end up thwarted by generation after generation of heroes. This all turns out to have been a scheme of the gods, who needed his knowledge to avert the return of the magical Cataclysm that started with his original death.

Live Action TV

 * Irina Derevko on Alias was an unfortunate victim of this trope. In season two, when she was, it was explained away as Irina playing a role for Khasinau, who thought he was the real leader. Her betrayal of Jack Bristow was also subsequently explained as her being an unwilling pawn of the KGB, forced to marry an American agent to find out about Project Christmas and then fake her own death. During Sydney's  , she and Jack team up to hunt for their daughter. When it becomes known that  , she becomes a valuable asset to the CIA, and rather than let them take her back into custody, Jack lets her go. She repays him by helping deliver Sydney's daughter, even though she really has been trying to kill them both as part of her "plan". After all these shades of gray, she's revealed in the series finale as your stereotypical Card-Carrying Villain,
 * Warren Mears was subjected to this in between seasons five and six of Buffy the Vampire Slayer. He built a subservient robot girlfriend because he was lonely, but found that he actually preferred a real-life girl who was his intellectual equal and "gave him a hard time". Xander even expressed sympathy for him (although he was undeniably a pervert). Yet by season six he's a full-out misogynist who Xander "could see as a Super Villain type."
 * The writers had originally planned to bring back Tucker Wells as the leader of the Trio. Notably, his troublemaking episode ("The Prom") was distinct from Warren and Jonathan's ("I Was Made to Love You" and "Superstar," respectively) in that it was intentionally malevolent as opposed to merely irresponsible. However, they couldn't get the actor. Ergo, Warren's "promotion" -- and part of the story behind the gag of Andrew only being known as "Tucker's brother".
 * Faith is another example. In the heat of fighting, she mistakes a passing human for a vampire, and stakes him. What Measure Is a Non-Human? is a big deal to Buffy & co, because they really freak out about this. When it transpires that he was connected with the Mayor, she argues that killing him wasn't that bad because he was a bad guy anyway. Only the audience, not the other characters, are shown how upset she actually is by the incident. Then, within a short time, she's working for the Mayor, and the reason for her switching from his enemy to his Dragon is never really explained beyond 'she's evil now'.
 * Faith's slide from the heroes who excluded and distrusted her to the villains who appreciated her was clearly marked and a matter of Character Development. But after being very clearly conflicted, she switches to acting like she was completely evil all along, and the 'good guys' treat her as if that were true.
 * Mandatory Doctor Who example: When they first appeared, the Cybermen, who at the time appeared roughly half-human, not mostly machine, had plausible motive for their villainy: they had become fixated with survival at all costs. By their fourth appearance the rails had begun to come off this idea and from then on, they've have various different motivations ascribed to them.
 * There's also the Silurians, who in their first appearance were three-dimensional characters who had an equal claim as humans to live on Earth. Most of them wanted a peaceful solution to the issue, and it was just a few bad apples who led to it ending in tragedy. Their next appearance portrayed the entire race as genocidal maniacs. When a newly awakened subspecies of Silurians appeared in the new series some thirty years later, they shifted back to the original portrayal.
 * Farscape has a positive example. Captain Crais's original motive for hunting down Crichton was to avenge the accidental death of his brother. This was something a simple discussion with Crichton could have cleared up, so the writers let them have that conversation, but in the context of a duel to the death that left Crais angry for a better reason: John won the fight and nearly killed him. Later, when Crais had more or less Heel Face Turned, he had another new motive for getting rid of Crichton: they were both in love with Aeryn.
 * Well, that and to get revenge on Scorpius who stole his ship, publicly shamed him, stole his life mission, and forced him into being a fugitive of the Peacekeepers.
 * Also, Crais never tried to get rid of Crichton, specifically because Crais knew that he ever laid a finger on Crichton, Aeryn would never forgive him...and would probably kill him, too.
 * Sue Sylvester of Glee initially hated the glee club because it was taking funding away her cheerleading team, the Cheerios. It later becomes clear that the Cheerios have boosters who "write fat checks" which take care of most of their expenses, and it seems Sue's machinations to take down the glee club come from either a personal vendetta against Will Schuester or just a perverse love for stirring up conflict.
 * It was always more of "principle of the matter" kind of thing. Before the Glee club, the Cheerios were the only shining light in a highschool of mediocrity; the football hasn't won a game in years, most everyone grows to get a job and live in the same town, and by being the best of the worst, the cheerleading squad dominated. And Sue liked being on top, with all the control. Even in the first episode, Sue could see that the Glee club had potential, potential that would take the light away from her team (and her), so she did all she could to make it not happen.
 * In Heroes, Sylar's motivation has gone from "I want to be special" (first series) to "I have an uncontrollable Hunger which makes me lust after killing to get people's abilities" (second). By the third, though, he seemed to have decided that "this is just who I am and I'm happy with it." Now his aim seems to be simply Kill All Humans With Abilities - Danko points out that "if we succeed, you'll be the only one left", and Sylar just smiles and agrees. He doesn't even need to kill to steal abilities any more either.
 * The irony being that Sylar was an infinitely more interesting character before they decided to burden him with more backstory than Wolverine
 * KARR, from Knight Rider. In "Trust Doesn't Rust", KARR's villainous acts are clearly the result of his childlike understanding of the world being misled by two petty thieves, combined with the Literal Genie aspect of his prime directive of self-preservation. When he reappears in "KITT vs KARR", he is simply evil, lusts for revenge against KITT, and even seems unconcerned about his own survival. Neither Michael nor KITT find this odd, and the characters even know ahead of time that KARR is insane and out for revenge.
 * KARR always had an ego that KITT's existence threatened, and more importantly KITT had very clearly demonstrated himself to be a relentless and serious threat. Survival at all costs dictates a "either me or you" style vendetta to resolve the threat.
 * Could have been a result of damage done to KARR's circuitry either by the fall, by the ocean, or by "the mysterious benefactor who rebuilt him". It was shown a few times in the show that KITT was capable of being reprogrammed by turning a dial and messing around with the circuitry under his dashboard. KARR probably also suffered from this design flaw, but would kill anyone who tried to do so. It was mentioned that at least one person had died because of KARR, and that could well be the reason they died: they were trying to reprogram him. It was also shown that water in the various systems could disable them, and salt water is even less friendly to electronics.
 * Jedekiah from The Tomorrow People. In "Break Out", the shapeshifting android was not really villainous, but was perpetrating his apparently-evil deeds because he was under orders from a kind alien who mistakenly believed humans to be dangerous and barbaric. In his various reappearances, Jedekiah is simply evil, and obsessed with revenge, conquest, and the eradication of homo superior -- and the Tomorrow People already seem to know this to be his natural personality ahead of time.
 * A major plot point, and proof Tropes Are Tools, is Breaking Bad. By season three Walter's entire motive to be a drug dealer is gone. His family has abandoned him, the money is no use for them, let alone for him to spend, but he likes it and is trying to rationalize what he is and what he has done. Particularly notable is that when he finally gets to cook meth as a quiet day job with no thrills he requests Jessie back and spends an entire episode trying to kill a fly. Jessie, on the other hand knows he's just a bad man.
 * He tells himself that he's still doing it to provide money and protection to his family (who are clearly at risk, since he's gotten in so deep). But it's made clear that these are justifications to do what he wants to do anyway.
 * As of the season 3 finale, this appears set to change, as he has observed the consequences of his actions.
 * The TWOP page quote is a reference to the Motive Decay of Vladimir Bierko in 24. Bierko's original plan was to assassinate the Russian president in the name of their separatist cause and attempt to blackmail President Logan into not opposing them. Once Logan didn't fulfill his end of the bargain, he switched into all out revenge on the U.S. and CTU, culminating in taking over a nuclear submarine with the purpose of destroying several cities, his original goal forgotten. The stupidest aspect of this is that his subordinate, Ivan Irwich, went through the exact same pattern earlier in the season (being focused on his goal to assassinate the Russian President, getting betrayed by the US then seeking petty revenge on the US). Then Bierko makes his on screen debut...and immediately kills Irwich for deviating from their goals, the exact same thing he would do two episodes later.
 * In V the original series, which followed the mini-series and The Final Battle, the visitors seem to have abandoned their original plan to steal all of Earth's water and use the people for food and have instead chosen to enslave the people for some reason. Even though they still use people for food, this appears to be a secondary motive rather than the primary purpose as it was in the original miniseries.
 * It's not so much that his motive got decayed, more like retconned, but in Criminal Minds, the Serial Killer known as the Fox had something like this happen to him when he was brought back in the season five episode "Outfoxed". His crimes as revealed in his original appearance were breaking into the houses of families, then taking them all hostage and forcing them to treat him as the head of the household before eventually leading them down to the basement and killing them all, saving the father for last. In "Outfoxed" it was implied that he sexually abused the children he took hostage, and it was suggested that his crimes were essentially him lashing out at his abusive father and also at himself. In his first appearance, there had been no hint of a sexual component to his crimes and the reason given for his behaviour was that his wife and kids had left him and he was trying to recapture what it was like to have them, with him killing the families at the end because he knew the fantasy couldn't last.
 * Sons of Anarchy: Agent Stahl's obsession with bringing down SAMCRO, which went from normal case to full-blown obsession after she was brutally assaulted by a member in prison, who broke her nose in the process. By season two, she's forgotten all about bringing them to justice and just fucking with them for the sake of malice, right down to framing Gemma for a murder she did not commit.
 * In season three her motive seems to shift to ruthless ambition when she is presented with a once-in-a-lifetime opportunity to break a major IRA network in the US. She promptly starts to undo her frame-up of Gemma and starts to protect the Sons since she needs to make the case. She then quickly goes even further over the Moral Event Horizon than most of the 'bad guys' on the show.
 * At the end she seemed to be primarily motivated by a case of Break the Haughty when she can't resist betraying so she can show the Sons how their pride in club loyalty and brotherhood was just a lot of hot air.
 * Logan and Jessica in the TV series of Logan's Run start out on a trip to find sanctuary. They say they're looking for it so they can go back and tell other people about it so they don't have to die on Last Day at Carousel. However, as soon as they're outside the city, they go on all kinds of adventures, sometimes abandoning common sense to allow these adventures to happen, like in one episode, they meet a man who says he'll take them to his city, but they have to abandon their vehicle and weapons. They gladly agree, and of course, trouble follows. The whole time they're looking for sanctuary, they could just go back and tell the people in the domed city that there's life outside and that it will be rough, but it beats dying at 30. Instead, they keep looking for sanctuary.
 * The same could be said for the sandmen who chase the runners. One of them is told by a council of old men that he can join the council and grow old like they have done. This is appealing to the sandman because he thought he would have to die at 30. When he gets outside the city, he should have had an epiphany, "Hey! It's not deadly out here. I could live past 30 out here, too! And others could join me!" Instead, he goes on trying to catch the runners.
 * Lord Zedd and Rita Repulsa from Mighty Morphin Power Rangers suffer from this. They go from wanting to conquer the Earth to wanting to destroy the Power Rangers, or even simply just ruining their day. Sure, if they get rid of the Rangers, they'll be free to rule the planet, but their plans noticeably go from "This plan will provide us with an unending power source or ultimate weapon that will allow us to take over the Earth" to "This plan will ruin Kimberly's chance at joining the Pan Global Games."
 * Not forgetting that when Rita escaped her jar the second time, after being imprisoned in there due to Zedd taking over her Moon Base, she went from getting revenge on Zedd for imprisoning her via an overly complicated scheme involving marrying him to... Just... Sort of nagging him constantly due to his inability to kill the Power Rangers while she's just as unsuccessful at it herself.
 * Morgana from Merlin started season three as a vengeful young woman who was out to avenge her own people against the genocide King Uther had committed against those who used magic. Since finding out that she's moved from Well-Intentioned Extremist territory into flat-out evil, most recently manipulating her best friend's feelings for Prince Arthur (her own  who has never done anything to her) in order to try and assassinate her way to the throne of Camelot.
 * In the Little House On the Prairie episode, "Family Quarrel", Nels and Harriette Oleson have separated and Nels is living in the hotel. Doc Baker and Mr. Hanson get the idea that Mr. Hanson should go ask Harriette out on a date. The reasoning is that Nels will get jealous and will want Harriette back. In the next scene, Hanson is wearing a suit and carrying some flowers as he and Doc Baker walk toward the mercantile store. Doc Baker tells Hanson that now is a good time because Nels is out of town and won't find out. This subverts the original purpose, which was to make Nels jealous.
 * In the episode "Haunted House", Nellie and Willy dare Laura to go up to a haunted house. She runs away scared. Later, to redeem herself, she approaches the house again, but is discovered by the owner of the home. She ends up forming a friendship with the owner and never tries to prove her bravery again, even though it was an important plot point and her motivation for approaching the house in the first place.
 * In Galactica 1980, the episode Space Croppers begins with the Galactica's fleet being attacked by the Cylons. The Cylons destroy the fleet's food supplies. Boy genius Dr. Zee comes up with a plan to send Troy and Dillon down to Earth to get some supplies. Troy and Dillon pick a farm at random and soon find out that the farmer is having problems with the local growers' association. Instead of picking another farmer to get supplies from, the motive decays into helping this farmer out with his problems and the rest of the episode revolves more around helping a farmer than it does about getting food for Galactica.
 * In the Highway to Heaven episode For the Love of Larry, a man and his boy are missing. Johnathan and Mark find the dog that was with them when they went missing. The Sheriff runs into Mark and Johnathan and shows them a picture of the missing man and boy with the dog. They explain that they found the dog, which is now in their rented cabin. Instead of asking them to take him to where they found the dog (as a good place to start looking for the missing man and boy), the sheriff asks them to take him to where the dog is now and when they find out the dog is missing, they start looking for the dog. The motive decay here is that they stop looking for a man and boy and start searching for the dog while two people are still missing. What was finding the dog going to do?
 * The original motivation of Fox Mulder in The X-Files was to find his abducted sister. This actually weaves in and out of the story for a good four years, but then it's dropped nearly entirely. When he does find her, it turns out she was killed, not abducted, and is a ghost child running around a feild. What should have been the ultimate climax of the story arc becomes a little sidenote a few years before the series actually ends.

Tabletop Games

 * Horus in the Warhammer 40000 universe seems to go through this process as well. The recent spate of Horus Heresy books depict his descent into evil as being triggered partially by a string of unfortunate coincidences and partially as a result of going from "I will save the Galaxy" to "I will rule the Galaxy" to "I will destroy the Galaxy". His initial actions are triggered by the Emperor's near suicidal mysteriousness about what his intentions are once the Galaxy is united under his rule. Horus, not knowing what the Emperor plans to do and having been made aware of how the Space Marines are being increasingly sidelined, rejects this and accepts the idea that as superior beings, the Space Marines have a right to rule. By the time of the Siege of Terra however Horus seems to have accepted the Chaos gods and is mostly in it for horrendously evil gits and shiggles.
 * The Chaos Gods, like the Dark Side, are quite fond of decaying the motives of the fools who sign up with them willingly.

Video Games
"Kefka: Uh, what is it that you want?"
 * In the first Assassin's Creed, the Templars are - for the most part - an order of well intentioned extremists who want to strip humanity of its "free will" in order to bring about peace and stability. Their motives are made even more sympathetic by the fact that the events of the game take place during The Crusades. Yet in the sequel, they have all been reduced to card carrying villains who kick dogs with gay abandon, are motivated purely by their own greed and act only For the Evulz. The only possible justification (changes in the organisation between the Crusades and Renaissance) is lost when even the present day Templar doctor who watched Desmond in the first game behaves like more of a Bond villain in the second.
 * Motive Decay is possibly justified in AC:Brotherhood, as the player can actually read about the motive decay of the Templars through optional documents. It's clear that the Templars' original motive of taking away free will to create stability has decayed into a flimsy excuse for oppressing the lower class as a means of protecting the interests and prosperity of a small elite. It's true that the villains of ACII were particularly fond of kicking puppies, however.
 * The Robot Masters in Mega Man 4 were only evil because their creator was blackmailed by Wily and they were built for practical purposes. In later appearances they are simply evil. To be fair the Mega Man series was never big on plot.
 * Bob and George filled a plothole lampshaded this, with the explanation being that the Soviet government took Dr. Cossack's plans and sold them to Dr. Wily, presumably because he forked over the most cash.
 * There remains hope. The FMV game Super Adventure Rockman goes to great lengths to remind us that the Mega Man 1 Robot Masters were perfectly good without Wily's influence, and Mega Man 9 shows heartwarming images of its Robot Masters integrating into everyday life during the credits.
 * Sigma from Mega Man X started off as wanting to take over the world to create a golden age of Reploids. Over the games though, he eventually seemed to just want to mess with X and Zero, even saying "I will make X AND Zero MINE!". Then in X8, he suddenly switched to a goal of creating a new world populated only by his 'children', the new gen Reploids. And then there's Maverick Hunter X, an MMX reboot series, where Sigma's initial motivation was creating a new era and pushing Reploid potential. More like Motive Roulette than just straight-up decay.
 * Without going into too much detail, it's been suggested that this is a result of Sigma's motives not being portrayed with adequate clarity the first time around. The underlying notion of this school of thought is that Capcom's great crime is one of laziness, rather than randomness.
 * Illidan from Warcraft, though always a mentally unstable guy, attacked Shattrah City for no apparent reason even though they shared a common enemy in the Burning Legion. However, previously he had been portrayed as wanting to keep a low profile in Outland. This unmotivated attack fails, resulting in his best troops deserting him and Illidan being killed in a raid.
 * In Illidan's initial appearance in Warcraft III, he is freed from ten thousand years of imprisonment to help his people. You might think that had driven him mad, but he does succeed in saving his people . Then he is hired by the demon lord Kil'jaeden to destroy the Lich King before he regains his power . Illidan is stopped by Furion, Afterward, Illidan tries one last time to stop the Lich King, . Thus Illidan had been, at worst, a Well-Intentioned Extremist who rarely did anything not in his people's interest (even the original reason for his imprisonment was for keeping part of the Well of Eternity, which he felt was too useful to completely destroy, even if it is what brought the demons). Even in The War of the Ancients Trilogy Illidan, while portrayed as significantly more power-hungry, still wishes to save his people. Come World of Warcraft, however, Illidan is brooding on Outland as a Designated Villain with Informed Insanity. He is treated as if he was always a villain, carries the title "the Betrayer" (which he, in fact, mocked in the intro to the Frozen Throne, but it seems the writer's forgot that he was right), and most of the expansion revolves around fighting him and his minions, despite the fact that it is supposed to be about defeating the Burning Legion's Burning Crusade, whom he betrayed and is now using their weapons against them. To put salt in the wound,
 * The Betrayer title was given to him back during the war of the ancients, not after WC 3. Due to him first betraying the good guys to join the legion, then double crossing them when he realized they were to evil, then (in his people's eyes) Betraying them again by recreating the very thing that had started the war to begin with simply to feed his own addiction. Illidan really does have a hard time staying on one side for any length of time.
 * Kael'thas in Warcraft 3 was a sympathetic character who allied with Illidan because he had no other choice and wanted to save his people. In World of Warcraft, he has become a power crazed evil overlord and demon worshipper who would gladly kill off his people to ensure the victory of the demons. One of whom is the very demon that arranged for his people's decimation in the first place.
 * This trend has become somewhat of a joke in the Warcraft fan community. An increasing number of villains appearing in World of Warcraft were once heroes or otherwise well-intentioned characters who have suffered from Motive Decay, most often Hand Waved with the "insanity" excuse. How else are you going to find new storyline bosses?
 * Arthas has largely the same storyline -- he starts out making difficult and heartbreaking decisions  and devolves into becoming a simple insane Big Bad himself. He only averts this trope because his fall into insanity was planned from the beginning, rather than something that was tacked on.
 * Tidbits such as this quest item and Horde NPCs considering having their siege equipment "accidentally" go off and hitting the Ally base leaves one to wonder how much of Illidan's attack is motive decay and how much is propaganda against him.
 * For both Arthas and Illidan, as well as much of the plot of The Burning Crusade and Wrath of the Lich King, the 'decay' stems from no one ever reporting back to the Alliance or the Horde about what happened in The Frozen Throne. Which makes sense, since no one connected to either faction was involved at all in the events at Northrend where all this happened. If Illidan had thought to inform others about what they were planning and why, it's quite likely that he would've been able to rally support from both the Alliance, The Night Elves, and the Forsaken and easily stop Arthas. For that matter, if he'd thought to explain what he was doing, or why he was doing it, it's likely that Malfurion wouldn't have banished him in the middle of Reign of Chaos.
 * A decent point but in WC Reign of Chaos, it's pretty clear Furion wouldn't give Illidan the time of day, There was little left of the Alliance for Illidan to ally with, plus the whole it was being run by racist assholes. In WoW the two people that could talk sense into Illidan are disposed of. It still comes off as, "We need awesome bosses for the expansion packs... I know!"
 * in Neverwinter Nights went from defending the city, to taking vengeance on the people who didn't actually kill but she blamed for it, to having a vague plan to enter their citadel, to joining them and destroying the city she now blamed for the earlier spoilered event.
 * Though having a ten thousand year old lizard-person Mind Rape her every night kind of drove her a bit insane
 * Forcing a paladin to Tyr, God of Justice, to live with the fact that she's serving a city that demanded her lover be put to death out of a misplaced desire for "justice" over the plague debacle actually makes for a very good treatise on what should actually make a paladin fall.
 * While technically neutral, there's been major debate among fans on whether or not Scorpion from Mortal Kombat has fallen to this trope, all hinging on whether or not his ending in MK II came to pass; up until then, he had come back to slay Sub-Zero to avenge the death of himself and his family and clan, but according to the ending, he notices Subby spare an opponent, and deduces that it's not the same man (in fact, the guy's the original Subby's younger brother). If true, from then until MK 4, Scorpion swears to protect the new Subby as atonement, giving him a modicum of depth that proves he's not the revenge-crazed one-track-mind spectre he would be if the ending never happened. Of course, this is all rendered moot when Deception gave him a higher calling than simple vengeance, but even that was screwed up, and now he's on another revenge kick.
 * Happens often to the villains of Final Fantasy:
 * Zemus of Final Fantasy IV starts out a Lunarian Supremacist. By the time of the game proper, he's more into Kill All Humans. When his body is destroyed, his soul quickly becomes the personification of hatred.
 * Sephiroth in Final Fantasy VII initially turns evil after going mad from the (partly false) revelation about his origins and deciding to take revenge on humanity on behalf of his mother whom he believes to be a Cetra. After he falls into the Lifestream and floats there for a few years, he returns having decided that it's actually all right that his "mother" is an Eldritch Abomination (the one who nearly wiped out the Cetra), and decides to absorb The Lifestream to become a god and acquire ultimate power. Then Cloud defeated him for a second time. In almost every spin-off since Sephiroth is little more than Cloud's archrival, obsessed with defeating him but not before Mind Screwing him by pointing out how easily he can push Cloud's buttons. He did have a new plot to take over the world in Advent Children, but he set it aside in the climax for a duel with Cloud and his plan failed when Cloud beat him. The accompanying novellas reveal he didn't even have to recreate a physical body for himself to see his plan succeed, he chose to do it just to rub his rebirth in Cloud's face. At this point Sephiroth is little more than the personification of Evil Is Cool, striking iconic poses and dropping quotable one-liners about despair before going off to duel Cloud again.
 * Dissidia Final Fantasy has a subtle Lampshade Hanging of this--when Sephiroth senses Cloud approaching, he tells Warrior of Light he must "fulfill his obligation" and goes off to see Cloud. When they meet Sephiroth squares off to fight, but Cloud refuses because he doesn't see the point of fighting him anymore. No, really, he says "Fighting you would be meaningless. I'm tired of taking part in pointless battles." By the end of the game, his fixation on Cloud has grown obsessive.
 * Not to mention Kefka's assessment of him.


 * Meta Knight first appeared in Kirby's Adventure as a Worthy Opponent who got caught up in King Dedede's self-induced Let's You and Him Fight with Kirby. Since then, he's appeared as a Worthy Opponent, got caught up in another Let's You and Him Fight, appeared as a Well-Intentioned Extremist dedicated to ending Dream Land's lazy lifestyle, and even appeared as a Blood Knight protagonist.
 * This is lampshaded in Fallout 3. In the Hubris Comics building (a parody of Marvel/DC), you can find a letter to the editor from an irate fan complaining about how the new writer of Grognak the Barbarian has reduced the villainess "the AntAgonizer" from a complex, sympathetic antagonist to a 2-dimension cardboard villain. Later in the game, you can even use the argument to persuade a woman who has based her entire persona on the fiction Antagonizer character to give up her life of supervillainy.
 * Lady continued on her path as a Devil Hunter at the end of the third game (rather than go back to a regular life) because she had "a job to do that's far from done, which is to eliminate every last demon", to ensure that monsters like her father never came about again. Seems heroic, right? Too bad you won't be able to tell. The animated series has her saying that she stays with the job, not out of a sense of heroics or a greater goal, but because she has an insatiable need to kill things. That's that.
 * Trent Hawkins, the hero of Tyrian lampshades this happening to him. Originally starting out to get revenge on the Mega Corp that killed a close friend, he ends up getting pushed into to ever more dangerous missions often only tangentially related to anything he actually cares about. Eventually, by the end, when he realizes that he "doesn't even remember the name of his friend killed in episode one", he just decides to Screw This, I'm Outta Here.
 * From the beginning of the Crash Bandicoot series, Doctor Neo Cortex was motivated to Take Over the World by a combination of They Called Me Mad and abuse related to his short stature. From Crash Bandicoot 3: Warped onward, his schemes are mostly carried out as a service to his boss Uka Uka. At other times, he either specifically attempts to get rid of Crash (lampshaded in Crash Nitro Kart when Cortex ponders how he can defeat the Bandicoots before recalling his original world domination goal) or does what he does For the Evulz.
 * In The Legend of Zelda series, Ganondorf was revealed in Wind Waker to have begun his conquest/invasions intending to make a better life for his people by getting them a home that wasn't as harsh and uninhabitable as the Gerudo Desert. Unfortunately, as Skyward Sword implies,, resulting in a rapid decay of his motives from "a home for my people" down to "Omnicidal Maniac" in a matter of months whenever he tries.
 * To be fair, considering he did nothing to get his people out of the desert during his reign in Ocarina of Time, it would appear his motives were lost long before Wind Waker.

Webcomics

 * Thief from 8-Bit Theater stole only to pay for his father's medicine. After the whole issue was resolved, he kept being as greedy as ever. When pressed by Black Mage, he was asked "So shouldn't you, y'know, stop stealing?", to which the answer was a simple "No."
 * Of course, every single Elf is a total bastard. It's even part of their (stolen) national anthem.
 * An example in this comic from The Adventures of Wiglaf and Mordred, except the evil one is the one who was attacked, not the attacker.

Web Original
"Marik: "No, I don't want to kill you. I just want to destroy you a little is all.""
 * Marik from Yu-Gi-Oh the Abridged Series initially wanted to kill Yugi in order to take his screen time. Nowadays, Marik gets tons of screen time, even more than Yugi and his friends, yet he still tries to murder Yugi.
 * Justified both in-universe and out. Marik has never been quite sure of exactly what he wants to do to Yugi, and the show ultimately has to follow the basics of the original plot, albeit barely.

Western Animation
"You're probably looking forward to one of my erudite speeches about me, Megaframe, the new viral dawn, et cetera et cetera. But I'm afraid I'm going to have to disappoint you. There is no grand scheme here. This is about revenge."
 * In Spider-Man: The Animated Series, J. Jonah Jameson has a perfectly understandable and sympathetic reason for distrusting Spider-Man: his wife was killed by a masked assassin working for a mobster Jameson was about to expose, prompting him to start a crusade against people who wear masks and act above the law. However, in Mysterio's introductory episode, Mysterio, who has done next to nothing to earn anyone's trust and wears a mask himself, publicly announces that he's going to bring down Spider-Man... and is promptly lauded as a hero by Jameson.
 * Not to mention that he's the one responsible for creating The Scorpion, although he does regret it later.
 * Vlad in Danny Phantom starts out with a rather sympathetic backstory and an almost understandable motivation: Jack, through sheer idiocy, caused an accident that sent Vlad to the hospital for years, costing Vlad's chance at Maddie, who ended up marrying Jack. Later episodes started ignoring it; in an episode where Danny changes history to prevent Vlad's accident (giving him absolutely no motivation for turning evil), he still turns out evil for no apparent reason. One could argue it's really a matter of personality in that Vlad has an unhealthy means of obsession despite different time periods. It's implied Maddie still loves Jack (Past Maddie is giving loving eyes towards Jack) in the altered timeline while Vlad is hinted to be bitter even during his college years (he crosses his arms in frustration when Maddie doesn't pay attention to him). With Jack alive, it's motivation enough for Vlad to go completely apeshit to preserve his happy ending. Of course, in The Ultimate Enemy, Vlad is shown as actually being a rather caring individual (willing to adopt Danny after he's orphaned, and willing to help rid him of his human sorrow for what appears to be purely altruistic reasons). So make of him what you will. His motives still decay over time, with less and less focus being on killing Jack and taking Maddie/Danny as his wife/son and more and more on just screwing with Danny and being his antagonist. At first he was an antagonistic in a half "I'll train you" kind of way and in the end he just went straight villain.
 * The Floaty Heads in The Secret Show parody this. Every single time they show up they want something totally different. It's not commented on in the show, but it is on the show's website.
 * Macbeth from Gargoyles was an odd case - he only attacked the Gargoyles in his first appearance in an attempt to draw out the villainess Demona. By the end of that episode, the heroes had explained that she hated them too, which gave him no real motive to oppose them... yet every subsequent appearance found some excuse to feature him as an antagonist. First he went after a set of magical scrolls (that turned out to be diaries) that the Gargs had anticipated Xanatos would try to steal. Not once, but twice, he fought them under the Weird Sisters' mind-control -- with a third incident that turned out to be a decoy robot double built by Xanatos. In a World Tour appearance, they crossed paths without trading blows, parting on fairly amiable terms, but then he was opposing their friend King Arthur in an attempt to recover Excalibur. For two full seasons, he was a recurring villain, who never once had so much of an Enemy Mine, despite having no specific reason to oppose the heroes.
 * After their cover was blown world-wide, he did get a cameo as a TV correspondent promoting friendly human-gargoyle relations -- kind of funny since the experiences he'd had that were shown to the audience were almost overwhelmingly negative! But he doesn't hold Demona against the gargs as a whole. In the comic continuation he's becoming more of an ally.
 * Villains in Gargoyles tend to be more complex than your standard "tie the girl to the railroad track" fare. After the "City of Stone" arc, Macbeth's only appearances as a true villain were under mind control. He actually did have a valid reason to at least try to obtain Excalibur- he fit the prophecy as well as Arthur Pendragon did. And the episode during the world tour would count as a non-antagonistic appearance of the character.
 * Most villains in Batman the Animated Series, and to an extent the comics, had genuine motives in their debut appearances, but the motivations for their later crimes was mostly "revenge on Batman"; to their defense, most of them were crazy.
 * Batman actually brings this up himself with the Mad Hatter, who in his first appearance was a love-lorn geek who used his mind-controlling inventions to try and force a woman to love him. In the episode "The Worry Men" he is simply using his inventions for personal financial gain. Batman tells him that he has become nothing more than a petty thief.
 * Notably averted by the Scarecrow, who was always trying to carry out some twisted science experiment with the people of Gotham as his guinea pigs. When he did commit robbery and fraud, it was typically to obtain money to buy more chemicals.
 * The worst example is probably Clayface, who started out with the goal of getting revenge on Roland Daggett for causing his transformation, and in his second appearance was motivated by trying to get back to normal, both of which are sympathetic motivations that make perfect sense. In The New Batman Adventures, however, he had also become a petty thief.
 * He returned in Justice League however and only joined Grodd's group because Grodd promised him a cure.
 * Justified with the Batman Beyond villain Shriek, whose motivation did indeed shift from "commit murder at Derek Powers' request so I can keep my job" to "get revenge on Batman", but it's understandable because.
 * Kim Possible: "Mathter and Fervent" presented us with The Mathter; He began by terrorizing Go City with vaporizing weapons because he was refused funding for his "unethical mathematical experiments". But after Kim and Hego beat up his flabby henchmen, he decides to make Ron (who has done nothing whatsoever at this point) his personal archenemy for no apparent reason in less than two minutes after they first meet. That's got to be some sort of record. He even goes to the extreme of erasing Ron's existence from all the computer records and then tries to off Ron in person for good measure resulting in Ron being zapped with a ray that turns him into an "Anti-Matter Boy" who disintegrates anything he touches. Wow. Talk about Disproportionate Retribution.
 * Almost every episode that involved any of Team Go, and especially when in their own city, tended to fall hard into superhero world cliches. Just as Kim Possible was a show lampooning the spy genre, they had their own fun with the superhero ones with Team Go. Example, Kim and Ron pick out Hego as the manager of the Bueno Nacho within minutes (his Clark Kenting was weak). Having taken Ron as his arch was simply "how it's done, who am I to argue" and between the choice of Kim Possible, the super strong Hego, and the pathetic sidekick, who would you want to choice as your enemy?
 * The Fairly Odd Parents: The pixies, lead by HP, were a race that wanted to impose order on Fairy World and the Earth. Then, suddenly, in "Fairly Oddbaby" they teamed up with the anti-fairies, despite the fact that they're the complete opposite of order and randomly want to blow up the Earth.
 * Now admittedly Teen Titans was never the greatest at establishing concrete motives for its villains (with a few exceptions), but a particularly solid case of decay still exists in the form of Brother Blood. He starts out as your typical power-mad supervillain pimp, helped by the fact that he has psychic powers, but then degenerates into For the Evulz territory and his final Evil Plan involves--becoming exactly like Cyborg. Why? Because he's decided that Cyborg is simply the greatest thing since sliced bread, apparently, which winds up making Blood look rather pathetic.
 * Darkwing Duck averts this with most of its cartoonish super villains, but with Bushroot it follows this trope to hilt. Bushroot started his life of villainy to get revenge on the scientists who mocked him and destroyed his inventions, and to be with the one he loved. Some of his solo acts continued with his misunderstood lonely madman, such as trying to create sapient plants, but others are just plain supervillainy, like growing money to steal more money. Whenever he's teamed up with the Fiendish Five, or just partnering with another villain, any good side goes away completely. Quackerjack, on a lower level, switches from trying to rebuild his toy empire/getting revenge on the toys/businesses who drove him out of business, to just wanting to commit random acts of crime. Then again, he's insane.
 * The "growing money to steal more" plot of Bushroot's does still kind of fit with his misunderstood lonely madman motif, as he was using the money mostly to buy things for his plant friends.
 * Gargamel, being a true capitalist, originally wanted to melt The Smurfs to make gold (probably to fix up his junky old hut). For some reason, in later seasons, he simply wanted to eat the blue communists (kinda reminiscent of cannibalism). This was made fun of in Robot Chicken where he said he never was clear on his motive.
 * One episode of the actual series infamously lampshaded it with Gargamel saying "I DON'T want to turn them into gold! I DON'T want to eat them! Now I just want them DEAD!"
 * In Re Boot Megabyte went from conquest of Mainframe to personal revenge in season 4. He even admits it during a monologue right before the cliffhanger.

"Commander: But if you do that, we won't be able to go back.
 * At first, it seems Wile E. Coyote of Looney Tunes wants to eat the Roadrunner. typical predator/prey relationship. But, some of the things Wile E. plans(poisoning, exploding, etc.) would make the Roadrunner inedible. He just wanted that bird dead after a while!
 * Chuck Jones would often quote George Santayana's definition of a fanatic - "someone who doubles his efforts while forgetting his aim" - in describing Wile E.
 * On Pearlie, the titular fairy's evil cousin Saphira would frequently come up with schemes to undermine Pearlie's credibility and get her kicked out of the park (so she could take over). While this popped up occasionally as the series progressed, in later episodes her schemes were usually either attempting to show up/embarrass Pearlie, or get revenge on one of Pearlie's friends (usually Opal) for various trivial reasons
 * Comes into play with Gorath and the Glorft's motives in Megas XLR. The whole point with Gorath coming back into the past in the first place was so that he could retrieve Megas and go back to the future and finalize the conquest of humanity that had been mostly-achieved when he left, but he jumps very cleanly into motive decay in the season 1 finale, where he resolves to destroy the Earth in the past.

Gorath: Then we won't go back!"


 * Baron Zemo from The Avengers: Earth's Mightiest Heroes initially strives to kill Captain America, then extract a Super Serum. This would not only help Zemo create powerful subordinates, but also cure him of Virus X, which deformed Zemo after Cap stopped him from using it as a weapon against the Allies. Then the Enchantress (falsely) offers to help him Take Over the World, so he and she go round up a supervillain team, and Virus X never receives another mention, up through Zemo getting re-arrested.

To find the half-life of motive decay, we multiply the number of writers, times time, times the number of characters. Know that different characters decay at different rates. Now turn your books to page 42.