Heel Face Index

"You can't believe all the things I've done wrong in my life.

Without even trying, I've lived on the edge of a knife.

When I play with fire,

I don't want to get myself burned.

To thine own self be true,

So I think that it's time for a turn...."

- "Burn In Hell" by Twisted Sister

Tropes about characters shifting on the morality axis, redemption and corruption. See also Betrayal Tropes.

See Sorting Algorithm of Face Heel Turning for a sheet of factors figuring into the probability of a turn.

Good to Evil
An adaptation of a work makes a character much nastier than they were in the source material. A character set up to be the more 'charming' type of evil is revealed to be much nastier than their initial impression. A character who undergoes prolonged torture gives up on their ideals and morality and joins Team Evil. Sometimes that niceness is just a facade. "Sometimes" because sometimes Good Is Not Nice. Every now and then, snapping The Pollyanna's mind just MIGHT turn her nasty. Either, technically, but good to evil is more common due getting more Shocking Swerve out of Good to Evil. All attempts at a genuine Heel Face Turn unsuccessful. Gritty reboots often turn a formerly straight-laced hero into someone more grey and Anti Heroish. Where the character doesn't care that they're about to turn evil. A normally level-headed character gets a taste of power and becomes a Jerkass. Evil is just so orgasmic that a character can't control themselves. A character crosses the Despair Event Horizon after learning that their religious beliefs are fake or mistaken. Except not really turning, it just looks like it. A once-respected hero for some reason or another turns evil, which often sets up a Cry for the Devil. A character sees or experiences something they were not meant to know and goes insane/evil. Mentally steeling yourself to fight evil eventually erodes your ethics. A character who breaks the commandment of Thou Shalt Not Kill suffers a karmic or moral backlash, or indulging in Revenge breaks the last bit of their sanity. A character goes evil VERY quickly after doing some warned-against but other innocuous thing. A character doesn't consciously realize how evil they are inside until later. When a character steps outside the bounds of ordinary, safe villainy into something outrageously EVIL. Rape used as a stock Moral Event Horizon. A character reveals that there was some willingness to their Brainwashing, hinting at or exploiting some inner darkness that is now at the surface. A character is so evil all along that they don't even need to have their mind broken to be useful to Team Evil. A comedic, laughable villain is revealed to be much more threatening than people thought. Where even a savior figure can become evil, because of the drama inherent in that. When having morally shady friends compels an otherwise nice or ethical person to do something they normally wouldn't in order not to let down their 'friends'. Surprise! That innocent fellow you were following from the start is now a villain. The mentor figure (usually good) laments that the person they trained used to have a good heart, but no longer. That ally of yours you left for dead? Yeah, the Big Bad got a hold of him and decided it was a good idea to twist him into his Dragon. A once-respectable, if persistent, opponent gradually becomes more evil, turning their existing antagonism/competition into something more serious. A heroic protagonist in a previous story is now the antagonist for some reason or other. Demonization renders a heroic character bad in order to suit the author's purposes. A heroic character becomes an outright villain in a sequel to a work. The tale of a character's slow but inevitable plunge into black villainy. A normally morally-upright character is shown to be indulging in some evil behavior as an advertising technique. A character is forced into evil by gambling debts to a criminal organization. A character, not quite a Heel yet, is rapidly being pushed in that direction. The story calls the hero out for doing something morally shady; unless The Hero takes immediately steps to correct their behavior, this is often the first step towards a full Face Heel Turn. Someone's mind is broken by the great power they suddenly possess. A Butt Monkey or Woobie turns evil in order to get the respect they want.
 * Adaptational Villainy
 * Bait the Dog
 * Being Tortured Makes You Evil
 * Beware the Nice Ones (sometimes)
 * Break the Cutie (sometimes)
 * Character Derailment
 * Chronic Villainy
 * Corrupt the Cutie
 * Darker and Edgier
 * Despair Event Horizon
 * Drunk with Power
 * Drunk on the Dark Side
 * Face Heel Turn
 * Faith Heel Turn
 * Fake Defector
 * Fallen Hero
 * Go Mad From the Revelation
 * He Who Fights Monsters
 * If You Kill Him You Will Be Just Like Him
 * Jumping Off the Slippery Slope
 * The Killer in Me
 * Love Makes You Evil (can be related to the Green-Eyed Monster)
 * Moral Event Horizon
 * Rape Is a Special Kind of Evil
 * More Than Mind Control
 * Not Brainwashed
 * Not-So-Harmless Villain
 * The Paragon Always Rebels
 * Peer Pressure Makes You Evil
 * Protagonist Journey to Villain
 * A Pupil of Mine Until He Turned to Evil
 * Reforged Into a Minion
 * Rival Turned Evil
 * Rogue Protagonist
 * Ron the Death Eater
 * Sudden Sequel Heel Syndrome
 * Start of Darkness
 * Super Dickery
 * Trapped by Gambling Debts
 * Villain Corner
 * What the Hell, Hero?
 * With Great Power Comes Great Insanity
 * Who's Laughing Now?

Neutral to Aligned

 * Adopt the Dog
 * Neutral No Longer
 * Awakening the Sleeping Giant
 * Heroic Neutral
 * Default to Good

Evil to Good
When a Knight Templarish organization as a whole goes from evil to good, or at least to A Lighter Shade of Gray). When a bad guy defects because he's sick of Team Evil. The fanbase or an in-universe crowd sees the character as a hero, but it's all in their perception Mook or Dragon defects to protect people s/he cares about. A candidate for Complete Monster is shown not to be one because there are lines even THEY won't cross. Neutral Selfish or Stupid Evil characters discover their morals in order to cooperate with others and save their lives. A villain realizes the error of his ways and prepares for punishment from the hero. Instead, the hero lets him go and tells him to atone for what he's done. A villain learns that being good leads to greater happiness. A villain fakes his or her conversion; essentially the inverted Fake Defector An entire race of people goes from evil to good. An evil character admits that his/her actions are evil. A character's Heel Realization delivers a weight of remorse, which may drive him/her toward the path of good. An overwhelmingly powerful villain becomes merely on par with the other heroes after joining them. A comedic, ineffectual villain becomes Badass once they start fighting on the side of good. A demon (or any other sentient force) takes control of a person's body, but the host manages to befriend him, turning him into an ally. An evil character's potential for redemption shows when s/he sheds tears over an evil action. An ordinary villain has his threat and vileness neutralized by repeated failure and humiliation, becoming less evil. Which can result in an Ineffectual Sympathetic Villain. When the hero and the villain begin to operate more-or-less from the same side, while remaining rivals.
 * The Atoner
 * Author's Saving Throw (either, technically, but evil to good is more common)
 * Break the Haughty
 * Character Check
 * Comes Great Responsibility
 * Conspiracy Redemption
 * Curiosity Causes Conversion
 * Defector From Decadence
 * Draco in Leather Pants
 * Easily Forgiven
 * Even Mooks Have Loved Ones
 * Even Evil Has Standards
 * Fighting for Survival
 * "Get Out of Jail Free" Card
 * Go and Sin No More
 * Good Feels Good
 * Heel Face Brainwashing
 * Heel Face Mole
 * Heel Face Return
 * Heel Face Turn
 * High Heel Face Turn
 * Heel Faith Turn
 * Heel Race Turn
 * Heel Realization
 * In Love with the Mark
 * Karma Houdini (sometimes)
 * Kill Me Now or Forever Stay Your Hand
 * Love Redeems
 * Mistreatment-Induced Betrayal
 * Mook Face Turn
 * Monster Adventurers
 * Must Make Amends
 * My God, What Have I Done?
 * Power of Trust
 * Rape as Redemption
 * Redemption Demotion
 * Redemption Earns Life
 * Redemption Equals Death
 * Redemption Equals Sex
 * Redemption in the Rain
 * Redemption Promotion
 * Redemption Quest
 * Reformed but Rejected
 * Reformed Criminal
 * Rivals Team Up
 * Screw This, I'm Outta Here
 * Symbiotic Possession
 * Tears of Remorse
 * Villain Decay
 * Badass Decay
 * Villainous BSOD (if followed through)
 * Welcome Back, Traitor
 * What Is This Thing You Call Love?
 * Worthy Opponent

Either

 * Ambiguously Evil
 * Awakening the Sleeping Giant
 * Becoming the Mask (when pretending to be a Face or Heel is no longer pretending)
 * Breakup Breakout
 * The Green Knight

Characters introduced as a team have members discard their old alignments once the team dissolves. Where the turn is caused by a traumatic childhood incident. Letting it go unchecked tends to leads to a Face Heel Turn, treating it tends to lead to a Heel Face Turn. From one side to another, but not really changing alignment. "I'm bad. Now I'm good. But now I'm bad again. Wait, now I'm good again. No, wait....") A villain gradually discards the reasons why they became evil in the first place, either losing their sympathy if they keep at it or give up their villainy after no longer caring about their Freudian Excuse A character suddenly finds him/herself in a difficult position another is routinely in and realizes the hardships it involves. When a hero or villain has so many things go wrong at once that they lose faith in their old ways and explore 'the other side'.
 * Bring Them Around
 * Defector From Decadence
 * Epiphany Therapy
 * Face Heel Double Turn - one goes from good to evil while another goes from evil to good at the same time.
 * Freak-Out
 * Freudian Excuse
 * Going Native
 * Hazy Feel Turn
 * Heel Face Revolving Door
 * Karma Meter
 * Literal Change of Heart
 * Mirror Morality Machine
 * Morality Adjustment
 * Motive Decay
 * My Species Doth Protest Too Much
 * Sudden Humility
 * They Still Belong to Us Lecture
 * Tomato in the Mirror
 * Trauma Conga Line
 * Wild Card ("What side am I on, you ask? The side I'm always on: mine.")

where an alignment shift should occur but does not.

Even though the villain came and saved the day, it was only a temporary thing not caused by a change of heart. In universes with this in effect, it's impossible not to be defined as "evil". A character is set up to be redeemed through kindness or The Power of Trust, but it's shown that it didn't work at all. ("Hey, Skeletor - this is He-Man. Wanna go to the mall this afternoon?") The villain wanted to reform, but too late. "My God, What Have I Done??....Hell, come to think of it, I've done nothing." A character does something nasty to show how evil they are, but it falls flat because the victim seriously deserved it. The heroes Kick the Dog (or worse) in an inexcusable way without experiencing a Heel Face Turn, because War Is Hell and even The Hero can't maintain their goodness throughout it. A formerly-evil character almost reaches redemption... and then stuff happens that forces them back into villainy against their will. someone gradually come to evil. A character is saved from Bait the Dog or worse because their evil acts are glossed over by Rule of Empathy.
 * Enemy Mine
 * Easy Road to Hell
 * The Farmer and the Viper
 * Go-Karting with Bowser
 * Heel Face Door Slam
 * Ignored Epiphany
 * Kick the Son of a Bitch
 * Obligatory War Crime Scene
 * Post-Mortem Conversion
 * Redemption Failure
 * Slowly Slipping Into Evil
 * Villainy Discretion Shot