When a certain (allegedly) non-villainous character starts getting explicitly dark character development, they are being painted into the Villain Corner.

This new development can be either subtle or blatant, gradual or abrupt. The character can be an old friend of the protagonist, a friendly acquaintance, [[BrokenPedestal a former Mentor]], or any other type of automatically respected person; the character can even be the actual protagonist. It can involve the revelations of dark deeds from the character's past, or manifest in new actions or attitudes which go against the established grain. In any of these cases, the audience is not supposed to suspect anything evil about this person; indeed, there may not ''be'' anything evil about them, at least initially.

The key to this trope is ambiguity. Once a previously good character begins to undergo this treatment, the narrative typically will become increasingly mum about their actual motivations and alignment. This can serve as an unintentional (or intentional) LampshadeHanging, as it is a sure sign that we're [[AntiHero not dealing with the sympathetic character]] we started out with.

This tactic ''can'' be handled well, and can add nuance and intrigue to an established character, shaking up potential story arcs and fan expectations. But when executed poorly, a clever audience will have them picked out from the beginning like an oak tree in a beanfield, even if the other characters [[DevilInPlainSight don't see it]].

Compare KnightTemplar and WellIntentionedExtremist, which is where this trope often ends up. See also AntiVillain.
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!!Examples:

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[[folder: Anime and Manga ]]

* [[spoiler:Everyone]] in season 1 of ''HigurashiNoNakuKoroNi'' approaches the corner very subtly, and they [[HeelRealization realize]] it very abruptly.
* Quite a lot of ''CodeGeass'' is about Lelouch trying not to paint himself into the Villain Corner... and failing miserably. [[spoiler:In the end, he just gives up and acts like an EvilOverlord so the world can be at peace when he's killed.]]
* ''{{Naruto}}'': Sasuke. Originally he was just a slightly dark [[RedOniBlueOni blue oni]] [[TheWoobie woobie]], but the [[SmugSnake actual]] [[ManBehindTheMan villains]] gave him a [[NoHoldsBarredBeatdown gentle push]] toward the corner, [[JumpingOffTheSlipperySlope and,]] [[WoobieDestroyerOfWorlds well...]]
* ''Manga/{{Berserk}}'' does this to Griffith in the [[AdaptationExplanationExtrication anime]]. Where as in the manga, it's a ForegoneConclusion that he [[spoiler: sacrifices the rest of the Hawks and becomes the [[BigBadEnsemble Godhand]] Femto]], this fact is not shown in the anime. He's initially depicted as a quintessential KnightInShiningArmor and all around NiceGuy but gradually he starts showing progressively [[{{Blackmail}} darker]] [[AssassinOutclassin shades]] of [[KillItWithFire grey]]. Yet, even then he's never really depicted as full on villainous... [[spoiler: until the Eclipse happens]].

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[[folder: Comic Books ]]

* While it's no secret that Cassidy from ''{{Preacher}}'' was [[AntiHero never a saint]], beginning with "Dixie Fried" he started to act more bastardly than was common up to the point, and then came "All Hell's A-Coming" where we find out just how bad he really is, and for how long.
* The Ultimate version of [[spoiler:[[ComicBook/UltimateFantasticFour Reed Richards]]]], who had three interconnected miniseries dedicated to going off the deep end.

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[[folder: Film ]]

* Jean Grey in ''Film/XMenTheLastStand'', due to WithGreatPowerComesGreatInsanity taking effect.
** Charles Xavier himself is this in similar situations in the comics, particularly the story arcs "Deadly Genesis" and "Dangerous", both of which seem to paint Charles as being both a WellIntentionedExtremist and NotSoDifferent from Magneto. [[BrokenBase Fans are divided as to how well this works.]]
* This was done to Anakin Skywalker throughout the ''Franchise/StarWars'' prequels. Since these came out after the original trilogy, [[ForegoneConclusion this ended up being a surprise to no one]].
* The progatonist from ''Film/TheBrainThatWouldntDie'' ([[Recap/MysteryScienceTheater3000S05E13TheBrainThatWouldntDie as seen]] on TV's ''Series/MysteryScienceTheater3000'') is also the main villain. We're not supposed to notice at first, but given his first few lines of dialogue it's rather like [[{{Anvilicious}} staring at the sun]].
** The put-upon lab assistant in this film is given a similar treatment; he seems almost sympathetic until, suddenly and quite inexplicably, he cops a nasty attitude halfway through the movie, just in time for his KarmicDeath.

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[[folder: Literature ]]

* The ''TabletopGame/{{Warhammer 40000}}: {{Literature/Eisenhorn}} Trilogy'' uses this on purpose, to show how an Inquisitor can [[HeWhoFightsMonsters go from Puritan to Radical in the course of duty]]. It displays the slide as a series of decisions that gradually get more and more radical as time goes on (ie [[spoiler: summoning a [[DemonicPossession daemonhost]] to kill a [[HumongousMecha Titan]] - but only after exhausting all other options, even the one that resulted in the LoveInterest going into a permanent coma]]).
** Eisenhorn isn't really an example of a VillainProtagonist, as all through the series his motive was to protect innocent people (particularly those around him) and this didn't change a bit. Eisenhorn didn't change his motives but his perspective on Imperial dogma did change. The [[spoiler: irresponsible]] action that caused his death was [[spoiler: letting Pontinus Glaw live as a prisoner and giving him an approximation of a body rather than just destroying him]]. Hardly an evil action.
*** [[spoiler: And...now he's alive, and working for the bad guys. Yup. Villain Corner.]]
* In ''Literature/TheDresdenFiles'' books, [[spoiler:Harry's mentor and teacher Ebenezar [=McCoy=] turns out to have a license to kill... and in fact to break any rule of magic he damn well wants to. However, he's not shown to abuse this power; the ambiguity comes solely from Harry's realization that the laws of magic aren't as black-and-white as [=McCoy=] taught him]].
* Delivered somewhat in ''Literature/HarryPotter'' (it turns out not quite as outright villainy, but as [[spoiler: OmniscientMoralityLicense]] and [[spoiler: really bad youthful influences]]) via a surprising instance of PosthumousCharacter.

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[[folder: Live Action TV ]]

* Series/{{Angel}}, in Season Two
** And again after they take over Wolfram & Hart. [[spoiler: The second time though, he was doing it to intentionally mislead the bad guys into thinking he had been corrupted so he could infiltrate their inner circle]]
* Based on the most recent episode, Henry from ''{{Series/Eureka}}''
** Averted in that he didn't do anything truly villainous, and continued to stay the same friendly face he had been. Truthfully, all he did was take more of a DarkerAndEdgier turn.
* Lex Luthor has undergone this treatment in ''Series/{{Smallville}}''. [[ForegoneConclusion We already know]] [[FaceHeelTurn where that one is headed]].
** As of S9, Chloe Sullivan seems like she's on that path as well.
* Peter from ''Series/DegrassiTheNextGeneration'' is in and out of the Villain Corner like a grade-school dunce. In his first appearance, he's a blackmailer; afterward the show desperately tries to make him seem like a good guy (including mandatory FreudianExcuse). But then he has several more KickTheDog moments, most notably when he helps a pedophile stalk somebody... and then an additional season of "no, he's really a decent guy." And after ''that'', (judging by promos) it looked like he was going to be evil again. But as it turns out, you can NeverTrustATrailer, and after one episode of appearing to be evil it turns out he's still good.
* In ''Series/{{Supernatural}}'' S4, one common complaint was that it was impossible to empathize with Sam for [[spoiler: betraying Dean and siding with Ruby]] because not enough was done to reveal his motivation for it. Ultimately, Sam was [[spoiler: briefly]] an example of this trope, and this point has been addressed in S5.
* [[spoiler: Gaeta]] in the finale season of the ''Series/{{Battlestar Galactica|Reimagined}}'' remake. His motivations (and emotional breakdown) are made clearer if one has seen the webisodes.

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[[folder: Webcomics ]]

* In ''Webcomic/TheOrderOfTheStick'', the wizard Vaarsuvius began showing signs of JumpingOffTheSlipperySlope after the defeat at Azure City left [[AmbiguousGender him (her?)]] suffering from BadDreams over the [[MyGreatestFailure failure]] of [[IncrediblyLamePun hir]] arcane power to save the day. It started with being a JerkAss to the rest of the party, progressed to [[spoiler:casually murdering SmugSnake Daimyo Kubota and then threatening to kill Elan]], and finally to a full-blown [[spoiler:DealWithTheDevil]] that eventually led to a near [[spoiler:genocide of the Black Dragons]] that very nearly pushed hir over the MoralEventHorizon. Fortunately, V shows signs of [[MyGodWhatHaveIDone desiring to redeem hirself]] at the end of the arc.
** The universe has made sure to give V another slap for the last action by revealing that [[spoiler: the family of black dragons and relatives s/he murdered were related to a large, powerful family of wizards that really got around, meaning V murdered people whose only sin was to sleep with a member of this family.]]
* In ''Webcomic/SluggyFreelance'', while Dr. Schlock was always more concerned with saving his own hide than anything else, still seemed like a pretty sympathetic guy until he took over [[OmniscientCouncilOfVagueness Hereti-Corp]]. After that, a storyline focusing on him was actually titled "A Year in the Life of a Villain."
* In ''Webcomic/TheWotch'', Miranda West has always been a {{Jerkass}}, but when she [[spoiler:transforms Natasha Dahlet of DOLLY into a [[AndIMustScream living, sentient dolly]]]] it's a pretty sinister act, even if it was delivered to a villain. Miranda's catapulting leap into the Villain Corner continued even further when [[spoiler:she ruined the life of a young man by permanently swapping his gender and then did the same to two innocent friends of his, just to point out how serious she really is about upholding the Masquerade.]]

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