The Killer Becomes the Killed

""But beware, for once you quench your bloodthirst,

Others will seek vengeance on you,

And they won't rest

Until you're dead.""

- Dethklok, "Murmaider" lyrics.

""Oh, he's a monster. A pure psychopath. So rare to capture one alive.""

- Frederick Chilton, on Dr. Hannibal Lecter

In a law enforcement procedural show, when the criminal gets away with murder or a similarly heinous crime, like serial rape (either through skill on his part or mistakes on those of the cops or the lawyers) but gets killed before the end credits roll, usually in a Vigilante Execution.

A subtrope of Karmic Death. Often goes with Serial Killer Killer. Often similar to Deus Ex Machina. See also Off on a Technicality for how they get out, and Vigilante Man for the sort of guys who kill this sort of guys.

In Revenge or Roaring Rampage of Revenge stories, making the killer the killed is the main goal of the protagonist, though he or she should be careful that he or she doesn't fall on the wrong side of the trope as well.

Anime and Manga

 * Light Yagami of Death Note has murdered hundreds, if not thousands, over the course of the series with the titular Artifact of Doom, only to be killed by the very deity that gave him the Death Note by making good on his promise to write Light's name in it.

Heck, none of the Kiras meet very pleasant fates. Two heart attacks, two suicides, and one burning to death, and that's before you consider the general misfortune they met with up until then.
 * Lelouch in Code Geass, foreshadowed from the very first episode: "The only ones who should kill are those who are prepared to be killed."
 * Does it really count if
 * Yes. Yes it does.
 * A Jerkass cyborg in Ghost in the Shell: Stand Alone Complex who got off a murder charge after turning the court case onto Togusa using excessive force for being 'prejudiced towards cyborgs'. The episode ends with a secretary on night shift watching a news report of both the man and his attorney having died in a hit and run car crash, while Boma enters from the car deck, informing her she needs to arrange for a damaged car being deposed.

Comic Books

 * In Sin City, Kevin is a Psycho for Hire / Serial Killer who murders and eats a number of women, before meeting his own gruesome end at the hands of Sociopathic Hero Marv. Also, Roark Jr, aka That Yellow Bastard, is castrated AND beaten to death by John Hartigan.

Film

 * In New Jack City, Nino Brown, a drug kingpin, almost gets away scot-free, when he's shot down by an old man who lived in the projects Nino took over to sell crack out of. Very dramatic, when the old man cries out "Idolater... your soul is required... in HELL!" and pulls out his gun and shoots Nino to death. As for the fact that Nino was on the escalator heading down, while the old man was on his way up the escalator next to him... What Do You Mean It's Not Symbolic?
 * This is also how L.A. Confidential ends. Ironically enough, the victim asks his executioner at the start of the film if he's prepared to shoot a hardened criminal in the back to prevent him being acquitted. Guess how the Vic dies?
 * Subverted in M, in which the serial child killer barely manages to be arrested, rather than killed.
 * Corpse Bride: No one bothers to interrupt Barkis' gloating over getting away with killing Emily to warn him that the goblet he uses to toast her is actually filled with poison, not wine.
 * In Suspect Zero, Ben O'Ryan is a serial killer who hunts down and murders other serial killers through telepathic "remote viewing".

Folk Music

 * The plot of the folk ballad "The Outlandish Knight" and its variations: "For six pretty maidens hath thou drown'd here/the seventh hath drownéd thee"

Literature

 * Used extensively in A Song of Ice and Fire. Due to the rogue's gallery of villains in the series, the monsters usually kill each other. For instance, Amory Lorch was fed to a bear by Vargo Hoat, who was then fed to the bear himself by Gregor Clegane, who himself was stabbed with a poisoned spear and became the subject of Qyburn's "experiments." Other villains, like Rorge and Biter, are killed by more heroic hands.
 * In Agatha Christie's Murder on the Orient Express, this was the killer's motivation.
 * And Then There Were None also has this as the killer's motivation.
 * Notable in that killer, though innocent before the events of the novel, recognizes that he is now a killer himself, and takes the only appropriate (for the trope) action.
 * In the Sherlock Holmes story "Wisteria Lodge", the killer escapes but is later murdered in Madrid. A couple of other stories close with hints that this trope may have occurred.
 * The Case of the Speckled Band crosses this with Karmic Death.
 * Regina's Song is about a girl who hunts down and kills the man who raped and murdered her twin sister (Along with a dozen or so other sexual predators who cross her path).

Live Action TV

 * Dexter is full of killers that were never brought to justice. And Dexter is the guy making sure that they die anyway.
 * Every Law and Order has a bunch of these. Some of them even well set up.
 * Inverted: In an episode of CSI, a criminal who the police have found clear evidence shot a teenager as he fled a shootout with the police in order to use his bike as a getaway vehicle is shot by a member of a rival gang as the police lead him away. The trope is otherwise played straight.
 * At the end of the second season of Veronica Mars, Aaron Echolls manages to get acquitted of the murder of Lilly Kane, mostly by virtue of the fact that he's, well, a famous movie star. He proceeds to spend the rest of the episode being smug at both Veronica and his son Logan, implying to both that he'll be around to antagonize them for a long, long time. Finally, he stumbles across one of his old movies on TV in his hotel room and seconds later is promptly shot in the back of the head by Clarence Wiedman, on orders of Lilly's brother Duncan (who Ecchols had accused of being the real killer, no less).
 * A variation of this trope is one of the ways a Columbo TV movie mixed up the formula a little. The killer the viewer follows from the beginning attempts to kill his rich uncle, but the uncle dies before his death trap is sprung... which kills the gardener instead. He eventually figures out who actually killed his uncle (his aunt), and attempts to blackmail her. Like most people who try to blackmail a murderer, he fails to realize that if she already killed one man, she's not going to have much problem with killing another...

Video Games

 * The principal antagonist in the videogame Condemned: Criminal Origins, is an embodiment of this trope. A serial killer who only targets other serial killers, killing each using their own quirky M.O.
 * Well, not ONLY other serial killers; he kills two cops, and frames the player character for it (and later plans to brutally kill the hero), then kills his own uncle and the mayor in the sequel.
 * Ragou and Cumore from Tales of Vesperia clearly fall into this trope. Ragou abducted people's children when they failed to pay his cripplingly high taxes and fed said children and many others to monsters. Cumore fooled people into working to death in slave labor camps and sent people on suicide missions hunting for a giant monster. Both got away with it due to being high ranking nobility... until Yuri slashed Ragou across the chest and pushed his body into the river. Later on, Yuri led Cumore by sword point into a quicksand bog where he was buried alive.
 * Mind you, in both cases it's Totally Awesome.
 * Hermes from The Suffering is a very interesting take on this. As a prison executioner, he made an entire career murdering people in different ways, but he stated that he was the only one focused enough to get the job. In fact, he was so focused that he gassed himself in the chamber, just to have knowledge of both sides of the "experience".
 * Case of the Ace Attorney series.
 * Also, case, though in a variation: