Faith Heel Turn

So there's this guy who is deeply religious, a Friend to All Living Things. Then, one day, he decides there is no God or tires of his prayers not being answered. Expect a lot of shouting. He loses all hope for everything, including human decency, and now he likes to rape puppies in his spare time.

Obviously, in Real Life, it takes a hell of a lot more than a loss of faith to just drive people to do evil. Done poorly, this can be an outright Strawman Political character to show that religion is supposed to be the sole moral compass for people.

Compare Hollywood Atheist (who experiences a much less drastic shift in his personality), Beware the Nice Ones, Fallen Angel.

When a character who gets religion turns good as a result, that's a Heel Faith Turn. If a character who gets religion turns evil, it's probably a Cult, Corrupt Church, Path of Inspiration or outright Religion of Evil.

Not to be confused with Faith's heel turn, becoming kill happy has little to do with atheism.

Anime and Manga

 * The Psycho for Hire Akabane of Get Backers (AKA "Doctor Jackal") used to be an actual doctor who saved people, but failed to save the son of a good friend. That is the origin of his current personality.
 * In Weiss Kreuz, Schwarz's resident Ax Crazy Knife Nut Farfarello started out as a devout Catholic child, but when he learned that he was adopted and that the nun who was his teacher was his biological mother, he had a psychotic episode and murdered his entire adopted family. As an adult he claims that his desire is to kill God, and spends his spare time torturing priests to death.
 * In the Soul Eater manga, pulls an ultimate Faith Heel Turn  because of imposed insanity from The Clown.
 * Rurouni Kenshin's Yukyuzan Anji is a particularly heartbreaking example, though he's not an awful person by any means. He turns from an extremely kind, devout, and physically unimposing Buddhist priest to the hulking fallen priest that he is in the Kyoto arc when the children under his care are trapped inside his temple and burned alive, due to his landlord being a dirty Jerkass.
 * Actually, it's worse: that wasn't 'his landlord'; it was the village head, hoping to curry favor with the new government and its emperor-centered Shinto. So he had the village burn down a Buddhist temple full of orphans. Based on actual history, after the Meiji cut off government sponsorship of temples to promote their new standardized form of the 'native religion.' The orphans are kinda a stretch, though.

Comics

 * This is the premise of the motivation for the Joker Captain Ersatz, Mr. Rictus, in Wanted, a kindly and religious man who was horribly scarred in a fire and, while on the operating table, died but found no afterlife.
 * The minor Marvel Universe villain Madcap went there first, save that he also got total immortality and superpowers in the same accident that killed his entire family and church group, making for even greater nihilistic nutsiness (though not nearly as much evil).
 * The main character from the title story of Will Eisner's A Contract With God is like this. Having lived his life as a good Jew only to lose his adopted daughter turns him into a slum lord.
 * Being Will Eisner, though, he makes it both convincing and tragic.
 * At least one Chick Tracts does this, possibly a few more. Act surprised.
 * The most perplexing (and unintentionally hilarious) example would have to be the one where a child grows up to become a Complete Monster...because he found out there was no Santa Claus. If you can follow the logic in that...well, I'm not entirely sure I want to know how you managed it.
 * A lot of FSTDT quotes feature people who fear having a crisis of faith because they believe this will happen.
 * One of the Buffy the Vampire Slayer Tales of the Vampires has a former priest vampire... who is fairly justified about his Faith Heel Turn, all things considered. Notably reversed in a Crowning Moment of Awesome for a certain Cloudcuckoolander.
 * The book Supervillains and Philosophy has an essay speculating about Two-Face's philosophical journey. (Obviously, this is a completely non-canon Alternative Character Interpretation.) According to this essay, Harvey Dent aka Two-Face was a believer in the strongly ordered universe of Calvinism when he was a young man. But when he went to college and learned about atheistic philosophies like Existentialism, he began to believe that his two-faced random destruction was more appropriate to the true nature of this chaotic world.

Films

 * In Bram Stokers Dracula, Dracula is originally a very pious nobleman, until one day, while he is busy fighting off the enemies of the Church, his wife kills herself. The priest tells him that, sorry, suicides are damned for all eternity, nothing to be done about it. Dracula does not take this news at all well.
 * Salieri in Amadeus does this after continually being upstaged by the boorish, spoiled, conceited, but vastly more talented Mozart, ultimately deciding to steal his work and drive him to his death, because he couldn't stand that God had made Mozart more gifted than he. Inverted in that even beforehand he was really a Jerkass whose faith in God was basically an extension of his personal vanity.

Literature

 * The Sparrow: Emilio Sandoz seems to have at the beginning of The Sparrow. Much of the book is finding out what exactly happened.
 * An inversion, but not a heelFaithTurn, occurs in Elantris with, whose growing doubts over his religious faith cause him to turn against the Big Bad. From the villain's perspective, this would be a straight example.
 * from Warrior Cats freaks out upon learning
 * A GK Chesterton mystery story involves the puzzle of why one person would murder another on the grounds of ideological agreement. In the story, a Hollywood Atheist has been trying to convince a Wide Eyed Idealist that all morality is merely subjective.

Live Action TV

 * Brother Justin in Carnivale starts out as a well-meaning preacher. However, some bad luck, combined with the influence of his loving sister ensures he ends up rather different.
 * In his case it was an unfortunate case of In the Blood, though.
 * Averted (or perhaps inverted) with Father Dougal of Father Ted. While Dougal often makes comments which would perfectly fit this kind of character (e.g. something like "Todd, we're not really supposed to believe in that Jesus stuff, are we?"), he is The Ditz and presented as a better person than the more faithful Ted.
 * Star Trek Deep Space Nine has a bit more gradual version: Kai Winn was always jealous of Sisko for being the one the Prophets chose as their Emissary, and the fact that they didn't communicate with her wore on her more and more. Then the Prophets' rivals, the Pah Wraiths, do show her some attention, and by this point, that's enough to drive her over the edge into true villainy as their servant, working alongside Gul Dukat.
 * Just so you non-Trekkies are clear here, the Prophets of this religion are very active figures, and it seems relatively easy to get a chance to contact one of them and receive knowledge. The highest member of the religion should certainly get this blessing from the Prophets, but Kai Winn never did. Ever. Probably because they see the future and know what she'll become.
 * Unless you count Orb Experiences, (which outside the wormhole seemed more vision and less communication), I'm not sure how active the prophets actually were.
 * ...which happened in large part because they did that...
 * Winn was an ass before the Pah Wraiths got involved; she got the job as Kai not because she was particularly devout, but because she had the political know-how to eliminate better candidates from the election. The Prophets probably ignored her because they realized she wasn't really in her position for the right reasons; to the Pah Wraiths, however, she (along with ) made an ideal Anti Christ.
 * An example where the person doesn't turn evil, but still gives up on life, occurs in the Star Trek Voyager episode "Mortal Coil", where Neelix dies and is brought back to life. He has no memory of experiencing the Talaxian idea of the afterlife (where you go to a forest in which you're reunited with dead loved ones). Because he lost his whole family in a war, that belief was the only thing keeping him going, and it takes Chakotay to talk him out of suicide.
 * Ryan Hunter from Joan of Arcadia apparently suffered one of these (of the Smite Me Oh Mighty Smiter variety) prior to his first appearance, leading to his becoming a church vandalizing, puppy-kicking anti-theist. Had the show survived for a third season, Ryan would've been Joan's Evil Counterpart.
 * An early episode of Stargate SG-1 had a religious guy go crazy and take over another planet with intense UV radiation as its god. What's particularly ridiculous about this is that no less than two of his teammates joined him. The one that didn't showed up in later episodes a few times, while the rest all died. Someone really fucked up the selection process for that team.
 * Used along with Heel Faith Turn in My Name Is Earl. A Scary Black Man gangster who went by "Hash Brown" and eventually became a priest ends up being on Earl's list at least five times, with each new list item revealed making him angrier and angrier until he snaps and decides to return to his gangster life. Then Earl recognizes his car and reveals that he broke the taillight on it (another list item). The broken taillight caused Hash Brown to get pulled over and be late for a deal which ended up turning into a brutal shootout, meaning that Earl had indirectly saved his life. Since this event was what had caused him to take up religion in the first place (he originally attributed it to divine intervention), he thanks Earl and goes back to being a priest.
 * In the Doctor Who episode "The Unicorn and the Wasp",.

Mythology

 * Older Than Feudalism: The Book of Job tests out and then averts this trope. Satan posits that Job is only a good, religious man because he is prosperous, and that if he suffered, would curse God. Satan attempts to test this theory to destruction. Job refuses to curse God no matter how bad the suffering. As a result, he gets his stuff back twofold. All the friends and family that died horribly around him, not so much.
 * It gets more jarring when you realize that the "new" wife, kids, etc. are working as a Replacement Goldfish for SEVERAL PEOPLE. Unless Job didn't care about which wife and kids he had just as long as he had them, in which case, what a Jerkass!
 * His wife actually didn't die. Many pastors have joked that her punishment was having ten more kids.
 * Judaism is kinda ambiguous on whether there IS such a thing as an afterlife, so it's not even clear that he got to see his original family after his death.
 * Job never sees his dead children. A sequence of messengers bring him bad news, but they could be misinformed or lying. If Job's original family is really alive, his later children aren't a replacement; they're an expansion.

Tabletop Games

 * Exalted has an unusually sympathetic example in the form of the Blood Queen, who used to be one of the Brides of Ahlat, an Amazon Brigade symbolically and literally Married to A God. The Brides of Ahlat are not permitted to sleep with any other man, on pain of death; a little-known fact is that this extends to rape. When the woman who would become the Blood Queen found this out the hard way, she renounced Ahlat, fled Harborhead, and became an akuma in order to take revenge on the entire institution that had ruined her life.

Theatre

 * This is a big part of the presentation of Salieri in the play Amadeus. Salieri starts out, as he tells the audience, a pious man living a staid life. His beliefs are called into question when he meets Mozart and doesn't understand why a borderline Jerkass like Mozart gets divine musical talent but he doesn't. Thus, Salieri renounces God, and actually experiences improvement in his status from that point onward.

Video Games

 * Grandia II has, who discovers that   and sets a plan into motion to resurrect the world's equivalent of Satan so he can destroy the world.
 * Vandal Hearts II has, who was intensely religious throughout all of his childhood and most of his adulthood, until . It wasn't enough to turn him into a coldly calculating supervillain from then on or anything, but
 * In the Assassin's Creed series, this is pretty much how the Templars fall after learning that.
 * Krelian and Grahf in Xenogears. Oh so very much. While Raging Against The Heavens, Krelian claims that, if there is no God, he will make God with his own hands.
 * Related to the Dracula example above, Castlevania's Dracula also renounces God after his wife died while he was busy fighting the crusades.

Web Comics

 * Gamzee Makara from Homestuck, who, upon losing his faith in the Mirthful Messiahs, decides that he needs to

Western Animation
"Ned: No, I'm not kidding. I'm going to sit right here and miss church. You just watch. [Smash Cut to Ned driving his car and looking Heavenward] Sorry, sorry, sorry, sorry, sorry!"
 * In the two-part Drawn Together episode "Lost in Parking Space", the devoutly religious Princess Clara is led to believe that the Rapture has come and taken her friends but left her behind on Earth. After she signs her soul away to a man she believes is Satan, she decides that she enjoys being evil and promptly goes on a rampage. When she discovers that the Rapture didn't actually come (her friends just ditched her to go to the mall), she changes back.
 * Bob the Cucumber in "Clum Babies" goes on a murderous rampage and kills the entire cast when he is told that the Bible is open to interpretation.
 * Played with on The Simpsons when Ned Flanders loses faith after his wife dies, turning the picture of God away from him and scaring his kids with his decision not to go to church.


 * Lampshaded in "Lemon of Troy" when Bart is handing out roles to the members of his team. He designates Todd Flanders "the quiet religious guy who ends up going crazy".