Undeath Always Ends

I see... only darkness... before me.

—Last words of Arthas, The Lich King, World of Warcraft

—Barbossa, Pirates of the Caribbean

The Undead are neither dead nor alive, nor do they last in that state particularly long. For whatever reason, most media showing an undead character with sentience will have said character not be undead by story's end. Sort of like Schrodinger's Zombie, they can only stay in an 'in between' state until observed in a movie.

Maybe they're tired of Immortality and choose to end their existence or cure their undead state, or embrace it so thoroughly they confuse eternal youth with indestructibility and get cocky fighting the hero. Whatever the case, undeath does not grant one the ability to stay alive no matter what ... well, undead no matter what.

Whether a vampire, lich, mummy, or rarer fare, you can rest assured that by the story's end any notable undead character will not be undead because of one of the following:

The character accepts their death or fulfills whatever duty kept them tethered to the world and rests in peace or ascends to the afterlife.
The character is killed by someone else (hero, villain; doesn't matter which).
The character, unhappy with his/her undead state, commits suicide or convinces the heroes to slay/vanquish/exorcise him/her.
The character kills himself or herself inadvertently.
The character dies in a Heroic Sacrifice.
The character is miraculously restored to full life.

It seems that not all undeath is equal - some undead are deader than others. More living undead, such as vampires, are less likely to fit this trope than less living undead (such as zombies). This trope seems to apply most strongly to ghosts, who are often called simply 'dead' even though they're technically undead. Vampires favor Suicide by Sunlight.

This is an (Un)Death Trope, so spoilers follow.

Examples of Undeath Always Ends include:

Anime

×××HOLiC and Tsubasa Reservoir Chronicle example- Yuko Ichihara. A full explanation would require an eight paragraph course in semi-made-up-by-CLAMP-mysticism, confusingness, multiple overly-complex-plan pileups, and would leave you more confused than educated.
Goes with the territory of the Kurosagi Corpse Delivery Service—the main character's power allows him to temporarily coax the recently dead to talk (and move) again in order to finish business they left on earth, but this effect's length can usually be measured in minutes before they're done and pass on again. Other characters who can revive the dead also exist, but their powers are equally temporary -- though in one girl's case it's because her powers cause the dead enormous pain and they become unreasoning monsters who must be put down.
Bleach's afterlife is a bit messy and it's a little hard to say exactly how it fits into this trope. For starters, there are Pluses, good spirits. They have three possible outcomes: A) Be sent to Soul Society by a Shinigami, B) Get eaten by a Hollow, or C) Become a Hollow yourself. For Hollows, you A) Get killed by a Shinigami, sending your now pure spirit to Soul Society, B) Get killed by a Shinigami, sending your evil-as-a-human spirit to Hell, C) Get killed by a Quincy, AKA, end of the line, D) Get eaten by another, stronger Hollow, or E) Eat other Hollows and eventually become stronger forms of Hollows. It becomes even more confusing when you get to the Soul Society...
Happens by the wazoo in Saint Seiya's Hades Saga. To both good guys and enemies.
Played with in My Lovely Ghost Kana--Kana is still a ghost at the end of the manga, but her time with Daikichi has made her feel more alive than ever.

Comics

Averted in any and all depictions of Casper the Friendly Ghost.
After Doomsday rips his arm off, Booster Gold bleeds out on the operating table - but contrives to do so during a period in which no one on earth can be born or die. Though clinically dead, Booster fights on with the help of a new suit of armour (incorporating a prosthetic arm) that his BFF Ted Kord rigs up for him. When the stasis period ends and death returns to the DCU, Booster drops dead - only to open his eyes again moments later, the suit Ted built having (unbeknownst to anyone but Ted) incorporated a life-support system that will keep Booster going indefinitely. This long period of undeath - during which Booster is basically a zombie in a tin can - ends when Booster strikes a deal with Monarch to heal his wounds and let him remove the life-support armour.

Film

The end of Let the Right One In averts this trope in that Eli is still "living" as a vampire at the end of the film. What's more, "she" now has Oskar with her whom she might turn into a vampire as well, or keep around as her new caretaker (it's never mentioned how old that father figure was when he first met here). It could be argued that before she met Oskar, Eli was unhappy with her vampiric existence, but meeting Oskar gave her a new lease on unlife.
At the conclusion of Corpse Bride, when Victor chooses to marry Victoria, the titular undead bride wishes them luck and then disappears into butterflies. Presumably she ascended to some higher plane rather than the afterlife seen in the movie.
Frankenhooker—a guy accidentally kills his girlfriend, and rebuilds her from parts of hookers he's killed. At the end of the movie, he is killed, and brought back to life by his girlfriend only with leftover hooker parts too.
In the movie Fright Night (1985), Jerry Dandrige (vampire) and his ghoul servant end up dead, and Charley's girlfriend Amy (turned into a vampire) is returned to life.
- But subverted in the movie's final frames, where we learn that Evil Ed was only playing possum.
After the possessed house in Monster House is destroyed, the spirit of the woman who haunted it is briefly reunited with her husband before departing into the afterlife.
Averted in the Eddie Murphy vehicle Vampire In Brooklyn. Early in the film Murphy's vampire recruits another character as a "ghoul" (basically a sentient decaying zombie) to serve him. After Murphy has been "destroyed", his body turns into mist and floats away. The "mist" laughs and drops his ring to his limo, flying off into the night. The ghoul, who is sat in the back of the limo, tries the ring on. This turns him into a vampire as well. So he is still undead by the end of the movie, but has received a complimentary upgrade to Undead Deluxe.
Averted in Shaun of the Dead. At the end of the movie, Shaun's friend Ed who was turned into a zombie ends up chained up in the shed, playing video games. All rather poetic, considering Ed was still "living" exactly as he had before dying. Much like a metaphorical zombie turning into a literal one.
- It all plays out like a comical kind of Reality Ensues - there's thousands of braindead, shambling bodies around the place, but everyone's got over the initial fear of them, so they start using them on gameshows and giving them menial jobs.
Innocent Blood: The original vampire tries to kill herself at the end, but is stopped.
Near Dark ends with the rest of the vampires dead and the main character and his love interest cured of vampirism through a complete blood replacement.
Averted in The Devils Backbone - although Santi accomplishes his Ghostly Goals, Dr. Casares becomes a ghost at the end, and stays that way.
Averted in Beetlejuice, where everyone stays a ghost.

Literature

In Frankenstein, it is implied that the creature committed suicide by burning to death.
In Bram Stoker's Dracula, the title character, his three vampire "brides" (who were probably turned years beforehand) and Lucy Westenra (changed into a vampire) are all killed.
Also averted with Discworld zombies, most of whom have jobs like policemen and lawyers.
Averted in the early Harry Potter books but then played straight with all but the house ghosts.
- Harry Potter has kind of a Sorting Algorithm Of Undeadness going on.
The plot of Stephen King's Pet Sematary circles around the concept that the dead should stay dead.
- And in fact they do. The corpses that revive after burial in the Pet Sematary are different creatures than the ones who died, the original owners are gone. The problem of the Pet Sematary is rooted in the desire to deny the reality of death, it's the 'come on' that enables the demonic power to get at them.
Xanth has the Zombie King. His power is to create zombies. They nearly always remain zombies, unless it's changed since I stopped reading the "Trilogy" after book 27. Oddly, the Zombie King is not himself a zombie; he was for a while, but he recovered.
- They do. The Zombie King is an unique case, all other zombies stay the same. But they are rarely more that scenery.
Death Knight Lord Soth from the Dragonlance books was turned Human and subsequently killed in the War of Souls trilogy.
- This also happened to Ausric Krell in the Dark Disciple Trilogy, he was turned Human by Mina. He was given some powers over undead by Chemosh to compensate for the loss of his Death Knight powers, but he was still defeated and killed by Rhys near the end of the third book.
Played with in World War Z. Near the end of the book, the "first generation" zombies are basically being worn down to nothing, but there's still no cure for zombism save a kiss goodbye, a stiff drink, and a bullet between the eyes.
Averted like all get out in Dragaera. Sethra Lavode is a vampire and intends to stay that way. Since she's so powerful that even the gods stay out of her way, she's likely to remain so.
- She did once tell Vlad that under certain (very unlikely) circumstances she'd consider her existence fulfilled and "become part of the rock of Dzur Mountain again".
Laura Moon in American Gods chooses death over undeath(or possibly full restoration) in the end.
In the end of Warm Bodies, some of the zombies (presumably the ones still intact enough to function) start to come back alive.
Mixed bag in the Betsy the Vampire Queen series: the vampires (mostly) survive, the zombie gets killed, and most of the ghosts go off to Heaven (or wherever), except for one who chooses to stick around.
Averted in Anne Rice's The Mummy, or Ramses the Damned. The Elixir of Life makes living creatures totally indestructible. If chopped to pieces, the parts will become independently animate. If incinerated, they will reconstitute. Naturally, the full ramifications of this are utterly horrifying once grasped.
Averted and played straight in The Death Gate Cycle. Prince Edmund frees many of the undead in a drawn-out campaign of attrition, but remains undead himself. Hugh the Hand is allowed to die before the final battle against Sang-Drax.
Gerald Tarrant, aka The Hunter, got nine hundred years of undeath thanks to a bargain with The Unnamed. But by the end of the third book, he sacrifices his life to defeat Calesta, and then the Mother of the Iezu restores him to human life for complicated reasons. And then he has a heart attack, but Damien heals him. And then his great-great-great-grandson goes after him for murdering his family, cuts off his head and throws it on a bonfire. It was a trick, and he walks away in the end.

Live-Action TV

Lost Double Subverted this- It was revealed in season 6 that the whispers heard throughout the show are the tormented souls of people who died on the Island and couldn't move on. In the DVD-only epilogue, however, Ben and Hurley bring Walt back to the Island, and it's heavily implied they plan to use Walt's powers to help the spirits, which include his father, move on.
Angel subverted this; much of the series was spent building up the fact that Angel would play a major role in the apocalypse, after which he would become human. However, he threw it all away at the very end to give two fingers to the demons who secretly run the planet.
- On the other hand, there is only the word of an evil demon that signing it away would really work. Even if it did, there is another vampire with a soul running around and the prophesy is ridiculously vague...
  - The After the Fall comics revealed that while Angel did indeed sign away his destiny, Wolfram & Hart never filed it. They still need him to flip out and kill everything.
Dead Like Me plays it straight, surprisingly. While the reapers are indeed undead and stay that way for decades, they do eventually get to go to Heaven—or a reasonable generic facsimile thereof. So do all the one-episode ghosts throughout the series.
Torchwood had a particularly disturbing variant on this: Owen is turned into a kind of undead in the middle of the series and remains that way for several episodes until the end of the series. He can't feel pain, can't eat or drink (since food just settles in his stomach), any wounds sustained do not heal (and have to be sewn up weekly) and worst of all, he can no longer have sex. At the end of the series, he "dies" when he is trapped in a nuclear reactor and his body literally melts into goo, with him remaining conscious until the very end.
In one episode of Buffy the Vampire Slayer a student from Buffy's school reanimates the body of his dead brother (who says he shouldn't have been brought back) and stitches together parts of different women to make him a girlfriend. Buffy and company are spared the moral dilemma of deciding his fate when a fire breaks out in the house and the corpse-brother dies while trying to retrieve his future bride.
- Buffy the Vampire Slayer implicitly averted this, given that vampires appear to be very hard for anyone but a Slayer to kill, and there generally being only a single Slayer at a time until first there is Kendra, and then Faith, and at the very end a few hundred of them. Soulless vampires are not depicted as suffering from the sort of remorse or ennui that would lead one of them to embrace being even deader, and they generally don't want to become living or believe they can.
  - On the other hand, the mythology of the show makes it clear that vampires have been around for about as long as humanity, but the oldest vampires we see still count their age in centuries. So either the ennui eventually gets to them, or the ones who are smart enough to live past 500 are pretty much guaranteed to be too smart to go anywhere near the Slayer.
  - One of the oldest vampires we do see is The Master, who is apparently a few thousand years old (hence why he looks so non-human). He is powerful and seems to find a certain joy in his undeath - which seems to suggest that vampires who live past 500 are simply very rare, and not really affected by ennui. Rare because, if a Slayer is killing several vamps a night, it all adds up eventually.
    - Whedon's script notes put the Master as being a little over 600. I don't recall any reference to his actual age on screen, so I've always taken that as Word of God. Has there been anything since?
      - Nothing explicit onscreen, but in the Master's flashback appearance in the Angel episode 'Darla,' set in 1607 (almost four hundred years prior to his death, making him just a little over two hundred at the time), he already had his fruit punch mouth. Maybe Angel (in his mid- to late two hundreds) and other vampires just wear their years better, but given that both the Master and Kakistos are said to be very old, to the point where they're taking on more animalistic features, the implication is that the vampire ages and takes on this or that aspect of an animal (the Master was a bat, Kakistos seemed to be a pig), but it takes many centuries. Though this may just qualify as Wild Mass Guessing.
  - Kakistos is very much implied to be much older than the Master having cloven hooves instead of feet and semi-hoof hands.
Kai from Lexx wins a game with the Big Bad to restore him to life, but Prince goes back on his word... or so we think. In the final episode of the series, he makes Kai truly alive - just so he'll lose his Made of Iron tendencies and become truly dead in the explosion when he takes out the other villains' asteroid-ship. Kai does not survive.
Constable Bob Fraser from Due South is able to move on in the Grand Finale, only after Benton brings his wife's murderer to justice.
Often averted in Ghost Whisperer, as there are some spirits that choose to remain Earthbound or to join with the mysterious dark forces that the writers seem to have forgotten they introduced back in the first season.

Mythology

This trope seems to stem directly from most concepts of an afterlife depicting it as something conveniently happening someplace far away where the dead can't bother the living anymore. The notion of dead people actually hanging around in the same world as the not-yet-dead thus violates the 'natural order', which of course can't be allowed to stand...
In folklore even Undeath by Choice never really works out. In Russian Folklore Koschei the Undying has separated his soul from his body, rendering him, well, Undying and then protected his soul with an elaborate series of wards. He goes on to get really-we-mean-it killed in *every* appearance he makes in folklore.

Tabletop RPG

The World of Darkness does this on a case-by-case basis.
- Generally, players of Vampire: The Masquerade or Vampire: The Requiem are going to want to keep their characters alive as long as possible, individually averting it. In the background material, few vampires are over a thousand or so years old (most of the canon characters are under 300), though this is less from ennui (the cure for that is the deathlike sleep called torpor) than from the backstabbing, predatory nature of Kindred existence.
- In Promethean: The Created, the Created want to end their undying, unliving nature by completing the Great Work and becoming human, but frankly, can you blame them? Even then, Mr. Verney, Frankenstein's Monster, is still going after several centuries, much to his regret. Note that, although Prometheans generally only get a couple centuries, "going to the wastes" (complete isolation from humanity and their powers) can extend this clock, which many take advantage of to extend their deadline to complete the Great Work; White Wolf leaves it open whether Verney and the other Progenitors (founders of Promethean lines) are truly immortal or just punctual about going to the wastes.
- In Mummy the Resurrection, the Undying spend time 'temporarily undead'. When they die for the first time, they're undead until they receive the Spell of Life, which returns them to true life and grants them Resurrective Immortality. Every time they die after that, their spirit spends some time in the Underworld before resurrection. It takes exceptional circumstances to finally kill them - utter annihilation or a genuine desire to die.
- The wraiths of Wraith: The Oblivion have three options: Oblivion, and utter destruction; Transcendence, and an ambiguous fate; or remain in the Underworld. Some older wraiths have been around for thousands of years.
As a rule, undead in standard Dungeons & Dragons are evil because they're animated by "negative energy." Even the completely mindless ones. Therefore, lesser undead tend to fall by the dozen before player characters, and greater (intelligent) undead are also in the queue to be eliminated eventually, usually as bosses of some stripe or another. Individual settings shake things up a bit more, with prominent lich and vampire NPCs in some, and whole nations that revere or employ undead in others.
- Eberron being particularly notable, where one nation, Karrnath, employs intelligent undead in its armies and whose king is secretly a vampire—and is in fact the most peaceful, caring monarch around (just don't threaten him, his people, or the peace). The elven nation of Aerenal animate "deathless," undead fueled by positive energy, as a living afterlife for their greatest citizens. There's also a semi-popular religion that reveres undeath as the path to immortality.
- Second Edition AD&D also had a unique form of Elven Lich that 'lived' for the sole purpose of hunting down other undead and destroying them. As this would clearly not be possible simply because they occur more rapidly than the elven kind can kill them, and that such endeavors are innately dangerous, it's not certain whether or not they would live that much longer than a normal elf would, especially in worlds where Elves can count their potential lifespans in millenia and not centuries.
- Shows up also in a host of Forgotten Realms modules and books, including several moments where the various undead elves complain about being dead for so long, despite canonically only approaching old age as an elf.

Video Games

D in Trace Memory moves on to the next life if you get the good ending. And in the second game, you lay to rest Kelly, Matt's Dead Little Sister.
All of the Unsent in Final Fantasy X and its sequel are eventually sent to the afterlife, generally by Yuna, willingly or not.
Heroes of Might and Magic 3: The end of the campaign does multiple versions, the revived king Gryphonheart kills his original murderer in a darkly humorous cutscene. His soul then leaves his body.
This trope is both played straight and averted in World of Warcraft.
- Named members of the Scourge are exclusively killable targets. At this point, even the Lich King himself has been killed. Kel'Thuzad was killed and arose as a lich in Warcraft3, was defeated in World of Warcraft, and then brought back once only to be beaten again, and Anub'Arak has been taken down, presumably for good.
- There is a quest chain devoted to bringing the lich Ras Frostwhisper back to life as a human... so he can be killed without self resurrecting.
- The Forsaken are clearly rotting, yet it seems that they'll stick around for a while given that they're a playable race. The death knights who turned against Arthas are also playable, so they're likely to remain undead as well.
- There are also undead whose age is measured in hundreds of years, like Dalar Dawnweaver (probable founder of Dalaran) and Meryl Winterstorm (founding member of the Council of Tirisfal), so it's unlikely that they'll be going away anytime soon.
  - In Cataclysm, Sylvanas decides to openly defy this trope after getting killed in an ambush and experiencing The Nothing After Death that Arthas mentioned. Once resurrected by her Val'kyr, she proclaims that she can't let herself or The Forsaken die off.
After being resurrected in the Shadowrun First-Person Shooter, you will explode if you die again, either from losing all your Hit Points (again) or from bleeding out after the teammate who resurrected you dies.
Beyond the Grave is an undead protagonist, has been undead for almost twenty years (though most of that time was spent sleeping), and stays undead throughout both games. The animation ends quite differently: he and Harry perform mutually-assisted suicide after realizing the flaws that led to their downfall.
Anyone who is resurrected using the life crystals in The Dig is generally killed off again very quickly, from the alien wildlife (you can resurrect an alien turtle, but he'll just get eaten or explode seconds later...or if you screwed it up, he'll turn into slime) to major characters like the Alien Inventor, who kills himself and seals himself inside a crystal after you're done talking to him, and Brink (as well as Maggie, if you choose to resurrect her), although Brink and Maggie's deaths are undone again at the end of the game.
This is a major plot point of Tsukihime. Dead Apostles, even though they're vampires, will eventually die sooner or later, so some of them have to get creative to extend their lifespans. Nrvnqsr Chaos does this by fusing with different beasts, Michael Roa Valdamjong does this through reincarnation, and Night of Wallachia does this by manifesting himself as a materialized fear or rumor.
Tales of Monkey Island: With the help of The Power of Love (and the Crossroads Exit spell), Guybrush comes Back from the Dead, and from his undead state, at the end of Chapter 5.
Zig-zagged in Professor Layton and the Unwound Future, in which Claire, was thought to be dead, is alive, albeit a few years later. But time travel is unstable, so she has to go back to the time she came from, and die.
This is the Underking's goal in The Elder Scrolls II: Daggerfall, which is why he seeks the Mantella, his heart.

Webcomics

Drowtales: "The dead should stay dead" is the Kyorl clan's attitude; we shall see if they were right....
In Erfworld, "uncroaked" units last for only a limited time before they decay. I don't know offhand whether that's a mechanic from any of the games that provide the general concept, but I wouldn't be surprised.
- Many strategy games give newly created undead a limited "lifespan" as a game balance thing - otherwise the side who can turn all casualties undead would get an unfair advantage in the long run.
- This is later averted by Prince Ansom and other "Decrypted" created by the arkenpliers.
  - Which, of course, proved it justified in the first place, as in Book 2, Wanda and her decrypted army are marching across the world nearly unopposed.
Averted so far in Sluggy Freelance. Supporting character Sam became a vampire back in 1998, and he's still a vampire, and still a supporting character. It helps that his attitude is pretty non-confrontational and he's the last surviving member of a vampire clan with a really obscure Kryptonite Factor.
In Scary Go Round, Shelley was murdered and brought back as a zombie, but became a normal living human again after being struck by lightning.
Averted in Indefensible Positions, where Dead Debbie, an undead protagonist, stays undead.
This is becoming a serious concern for Richard of Looking for Group. Whether due to the breaking of his demonic contract or growing desire for his abandoned humanity, Richard is slowly becoming more human each day. The only thing that reverses this is killing innocents, but he finds himself increasingly reluctant to do so.
In The Kingfisher, most of the vampires don't seem like they're going to fall into this trope... until they get older. The elder vampires find ways to die left and right.

Western Animation

The ghost of Cassidy from the second season of WITCH is eventually brought back to life and reunited with her mother. It's never explained how this happened or how everyone reacted to someone who'd been dead for several decades suddenly showing up again.