- They have become a Rival Turned Evil.
- They have lost perspective, becoming a Well-Intentioned Extremist or Knight Templar.
- Something horrible has happened that shattered their faith in good, and they have become a Fallen Hero.
- Lust for power and fortune at any cost has brought out their worst.
- Love has turned into a dangerously out-of-control obsession.
- No Good Deed Goes Unpunished: Too many of their good deeds having come back to bite them convinces them that being a hero is no longer worth it.
- Their allies have made life too difficult or out-and-out betrayed them.
- They've snapped after one too many rounds of being put through hell.
- Getting no thanks for their work or even a bad reputation instead pushes them into a Mistreatment-Induced Betrayal.
- Revenge has twisted them into something as bad as, if not worse than, their original enemy.
- They have gone Drunk with Power.
- They made a Deal with the Devil and did something truly heinous to cement their allegiance to their new master, turning on their former friends.
- They fell prey to The Corrupter/The Corruption, which brought out the worst in them.
- They spent too long in the villain's headspace or among villains, leading to Becoming the Mask.
- One or more villains made a convincing argument (and may actually be right).
- They committed a small act of evil, leading to more and bigger acts as the hero started Slowly Slipping Into Evil.
- Their Morality Chain was killed or seriously harmed. Or was abandoned or betrayed them.
- The other heroes collectively went through any combination of the above (while remaining protagonists), and they did not.
This is the Evil Counterpart to the more common Heel–Face Turn and is generally found in a story with Black-and-White Morality. The many reasons and the probability for a turn are listed in the Sorting Algorithm of Face-Heel Turning.
The term "Face Heel Turn" comes from Professional Wrestling, in which a "good" wrestler (a face) is occasionally tempted by The Dark Side, or just gets fed up, and becomes a "bad" wrestler (a heel). Magazines and other promotional material from the various wrestling "leagues" frequently comment on various wrestlers' changes in "alignment" (in wrestling's fictional plotline known as kayfabe) nearly as frequently as they actually cover events in the ring themselves. (They even use phrases like "Face Heel Turn", though the shorter "Heel Turn" is more common.)
A wrestler's heel turn is often a sign that he or she is about to see his or her popularity skyrocket. Indeed, it is very common, once they have turned, to remain heels for their entire careers. Heels that become really popular may end up "naturally" becoming faces again, but it is just as likely for heels to be beloved because they are heels. In fact, as paradoxical as it might seem, a heel turn can help an otherwise despised wrestler become likable: fans may well resent a face character, and may be better able to relate to a character who is profoundly flawed in one way or another. (After all, that's what satire is all about.)
Note that a Face-Heel Turn is harder to pull off than a Heel–Face Turn - at least convincingly. If a character is introduced as likable and heroic, it takes some good writing to properly take them through the Character Development required to become a villain. Simply Foreshadowing that a character could turn evil is not enough. The work has to be put in to get the character to that destination; there are plenty of wrestling examples where this hasn't been done, or the reasons for the turn are so badly thought out that the fans reject it, and the wrestler turns back face shortly after.
- The Mole: The Mole was always working for the Big Bad from the beginning, whereas a character making a Face Heel Turn was a genuine good guy until their change of heart.
- Forced into Evil, whereas the character was still a genuinely good guy, but had his own reasons to be on the bad guys' side while still maintaining a good heart, whereas a character who did a Face Heel Turn is a character who not only goes to the bad guys' side, but also become a genuine bad guy at heart. A character Forced Into Evil can be said to be about halfway froom doing a full Heel Turn, but not a full turn yet like the ones in this page (given time, however, they may make a full turn in the future).
- Face–Monster Turn, which has many subtropes. The character really has no choice about becoming evil, because they are Brainwashed, literally turned into monsters, are possessed, or some other reason.
- Fake Defector, where someone on the side of good infiltrates the villains' side by pretending to do such a turn.
- Evil All Along, in which the character was, well, evil all along, but not necessarily working for the villain, like The Mole.
Compare Protagonist Journey to Villain, a plot which utilizes this trope as the entire character and story arc. Big Bad Slippage, where the Big Bad does this over the course of the story, is a Sub-Trope.
See also Heel–Face Revolving Door, Neutral No Longer, Deal with the Devil, We Used to Be Friends, Start of Darkness and Et Tu, Brute?. If the turn takes place extremely abruptly, it may include Jumping Off the Slippery Slope. If after the turn, there are still past rivalries with their new potential allies they can't overcome, see Personal Hate Before Common Goals.
Due to the nature of this trope, MAJOR UNMARKED SPOILERS ahead!
In Real Life, the nature of Heel–Face Turn and Face-Heel Turn is subjective (one person's "heartless betrayal" is another person's "seeing the light", depending on what group the individual is going to or leaving). Therefore, No Real Life Examples, Please!
- Anime & Manga
- Comic Books
- Fan Works
- Live-Action TV
- Professional Wrestling
- Religion & Mythology
- Tabletop Games
- Video Games
- Web Original
- Western Animation
- In Pleasant Goat and Big Big Wolf: Mighty Little Defenders, General Wolf/Chapper used to be a friendly wolf who supported peace between goats and wolves with the help of his goat friend Gogoa. After he got shot with a laser gun, he thought Gogoa was the one who shot him (Gogoa was actually framed for it). A month later, Chapper woke up to find out that the wolf tribe had lost and the leader had died. Chapper found out that Gogoa had left Goats' Village and Chapper was not welcome in the village. These events turned General Wolf against Gogoa and the other goats and he became determined to get revenge.
- In the back story of Euripides' Hecuba, Achilles, hero of The Iliad, defected to Troy after falling in love with Trojan princess Polyxena. And then his would-be brother-in-law Paris shot him in his Achilles' Heel at the wedding, and everything went pear-shaped for the Trojans.
- Invoked by Pulitzer in Newsies, by threatening to have the Newsies arrested if Jack doesn't agree to end the strike. In exchange, Jack tries to argue against his own cause at the rally he organized, despite protests from Spot and Davey. Luckily, Katherine talks him down, and he relents.
- This is essentially the entire plot of Sweeney Todd: The Demon Barber of Fleet Street as the protagonist begins a sympathetic Anti-Hero, progresses into Anti-Villain territory over the length of the first act, and finally crosses the Moral Event Horizon with gusto by intermission, largely due to Sanity Slippage.
- Westeros: An American Musical: What is seen of Theon Greyjoy's story in the play can be summed up as this. When first seen, Theon is fighting alongside Robb and trying to petition his father Balon, an old enemy of Robb's family, to fight alongside Robb. Balon unfortunately decides he'd rather have a second round against Robb's family instead. Last Theon is heard of, he's reported to have captured Robb's hometown for Balon.
- Elphaba from Wicked fits this trope, after having everything she tries spectacularly backfire on her, and having everyone she loves die all around her, she snaps during the song 'No Good Deed' dedicating herself to a lifetime of evil. Almost immediately subverted when she is shown to be just very, very pissed off, but not actually evil a mere song later.
- Nessarose, her sister, goes from a bratty but well-meaning child to the Wicked Witch of the East who, unlike is closer to the the film's portrayal of her than Elphaba. She is named governor of Munchkinland and uses the position to strip away their power in order to keep her husband Boq from leaving her, and when he tries, she removes his heart, turns him into the Tin Man, and blames it on Elphaba. Likewise, Boq goes from a shy boy with a crush on Galinda to a far more murderous version of the Tin Man, who declares "for once I'm glad I'm heartless — I'll be heartless killing her!".
- Discussed in Double Homework. According to Marco, this is what happened to Dennis after he’d been fixing his classmates’ computers for no apparent reward.
- The Most Epic Story Ever Told in All of Human History: Epic Robot Guy is a good guy in episode three, "The Most Epic Superhero Origin Story Ever", who becomes a villain by the time of episode five, "The Most Epic Crime-Stopping Mission Ever". This is Lampshaded In-Universe with the text “he became a bad guy! Dun dun dunnn!” written next to him when he appears.
- Red vs. Blue: After one too many betrayals and being imprisoned after all his efforts to bring down the Director, Agent Washington snaps and decides to capture Epsilon for the Chairman so he'll finally be allowed to leave Project Freelancer and the UNSC behind, even if it means he'll have to kill the Reds and Blues to do it. Getting double-crossed by the Meta and having the Reds and Blues save him once more causes Wash to change his mind and realign with the heroes against the Director.
- According to Ozpin, Lionheart was a different person before joining Salem and he seemed just as loyal as Team RWBY appears to be in the present. The second season of RWBY The Grimm Campaign, which depicts the Kuchinashi incident and takes place two years before the beginning of the main series ends with him sending Huntsmen reinforcements to help deal with the Wave crime syndicate that's left in Kuchinashi after their leader is killed. By the start of the main series, he begins feeding Salem the locations of every Huntsman in the kingdom to have them all killed, and he enrolls Cinder's team into Haven Academy with forged transcripts so that they can sabotage Beacon Academy from within. During the Battle of Haven, he learns Oscar's identity and contemplates capturing him for Salem, hoping he can finally be freed from the torment of working for her. By then, he's become a person that Ozpin no longer recognises.
- Ironwood first appears as one of Ozpin's most trusted allies and someone who desperately wants to protect the world from Salem. The events of Volume 3 leave him traumatised from the way the villains exploit him and his army to harm Vale; he becomes increasingly authoritarian and controlling, such as closing the Atlesian borders and imposing curfews. Four volumes later, the heroes become increasingly concerned about his decisions until he finally snaps from a combination of learning that Salem can't be killed and the villains pressing his Trauma Button one too many times. Pushed over the edge into villainy, he fulfills Oscar's prediction of becoming as dangerous as Salem by temporarily replacing the Big Bad as Volume 8's Arc Villain.
- Supermarioglitchy4's Super Mario 64 Bloopers: Enzo. He used to be a friendly guy and was being nice to other people until in "Birthday Freakout", after Mario ruins his birthday party. From then on he becomes a villain and is determined to kill Mario and the rest of the main cast. He is also actually revealed to be the shady black figure in "The Visitor" (2014).
- Trick Moon: Prior to the events of the short, Mage trapped Prince in the Moonstone and left the group to join Dr. Bleak.