A Betrayal Fic is a fanfic where a character ends up betrayed by their close peers, lover, etc. This often leads into the one being betrayed starting new relationships with other characters, some that they might not even know in canon. The betrayed will invariably end up becoming a much stronger person (emotionally and/or physically) afterwards and reunite with their former friend(s) only to either call them out or beat them up.
The Betrayal Fic is extremely common in series where the main characters are True Companions. Breaking up a tight knit group is an immediate source of conflict and it allows for new character connections and a change in character direction for the protagonist.
Betrayal Fics are generally written in response to how the writer perceives the character dynamics in a work, with the character who was betrayed usually being the Butt-Monkey or otherwise someone who they feel deserves more respect from the rest of the cast, with the fic dedicated to showcasing what they can do when finally taken seriously. As part of this, the people doing the betraying tend to be ones the writer dislikes, in worst case scenarios being turned into Ron The Death Eaters in the writer's quest to emphasize how badly they treat the character in question, and make to it more satisfying when they're taken down at the end. This is not obligatory, however; despite what we just said, not all Betrayal Fics are Revenge Fics, and the writers might even be fond of the characters.
As this trope often involves major plot points, all spoilers are unmarked.
- Pokémon Reset Bloodlines features a parody and a Take That! against betrayal fics in Chapter 24, and further jokes in the story, its omakes, and authorial commentary makes it clear the author very much dislikes them. In the process of mocking them the fic covers most of the basics of the genre as written in Pokemon: an assortment of Ash's friends and rivals telling him he sucks and that he should stop training for making them look bad, attacking him and trying to kill him (and often killing Delia if she is not part of the betrayal), either taking all of his Pokemon away or the Pokemon (either all or many) joining in said mutiny, Ash running off to Mt. Silver or somewhere similar to train and become 'badass' upon returning later, etc. The main point not covered in the jokes is the near obligatory return being set at a world championship tournament.
- What A Wonderful Loss revolves around Misty and Brock abandoning Ash after he goes Disguised in Drag to the Celadon Gym. Even Pikachu and the rest of Ash's Pokémon turn on him. This causes Ash to turn to Erika for friendship and a romance soon blossoms between them.
- The Final Battle is a betrayal fic where Ash is accused of murdering several of his friends. It was a frame job done by Team Rocket to try to get him killed. Because of circumstantial evidence, he's convicted, and his escape and subsequent years on the run (so as to protect his Charizard, who would be executed as a dangerous pokemon) make him seem even more guilty. It's more of the softer type of betrayal fic, though, as Ash's former companions are still sympathetic and shown to have their doubts as to Ash's guilt, with Ash eventually beginning to forgive them as he heals from his own trauma.
- The infamously Grim Dark doujinshi Magical Girl Lyrical Nanoha BetrayerS is set in an Alternate Timeline where a sudden proliferation of mass-based weaponry on Midchilda and the Bureau's apparent inability to deal with it, causes Hayate, Nanoha, and several other main characters (notably excluding Fate) stage a coup, taking over Mid and becoming known as the "Betrayers" to the mages who stayed true to the old Bureau's ideals.
- Very common in Naruto fics, with there being writers that ONLY do Betrayal Fics. The most common are fics where the titular character is betrayed by friends and teammates, though you can easily find one with any combination of characters:
- Sakura's Determination is about Sakura awakening a kekkei genkai (which allows her to copy bloodlines and makes her immortal) after being betrayed by her teammates.
- Wrath of the Crimson Uzu is a Sasuke-bashing revenge fic where Naruto is thought to be dead after being betrayed by Sasuke during the fight with Haku. Four years later he comes back home super angry and ultra powerful.
- Sailor Moon:
- Usagi is Dead is a 1997 fanfic where the Senshi kill Usagi so that Naru can take her place. Afterwards, Usagi ends up brought back to life.
- At the start of Her Love, Usagi sees her boyfriend Mamoru kiss her best friend Rei. When Usagi runs to the other Senshi for support, she overhears them complaining about her behind her back. Demande (or "Diamond" as he's called) ends up finding Usagi and comforting her.
- Betrayed revolves around Usagi being betrayed by her friends. They think she's a terrible leader and so they want her to give up her Transformation Trinket. Usagi overhears them, which causes her to go solo.
- Like the Naruto examples listed above, there are an astonishing number of stories in the Fairy Tail fandom where, for various reasons, Lucy is removed/kicked out of either Team Natsu or the guild as a whole. Often this is done to make way for Lisanna, who's typically characterized as a much worse person than she is in canon to make Lucy look better despite Lucy already being the character the reader is meant to sympathize with.
- Soul Eater fanfic "The Ultimate Betrayal": Crona, of all people, reveal that he was Evil All Along and collected the information he needs to destroy the DWMA and Death himself. When angered Maka tries to beat him, she was stopped by Medusa, who is good mother in this story.
- My Little Pony: Equestria Girls dealing with the fallout of Anon-A-Miss, the cyberbullying plotline of the 2014 IDW Holiday Special comic book. Most of these also cross over with Fix Fic that change the ending, depending on how much the author of the individual fic wants to demonize the culprits or the rest of the Equestria Girls:
There's been more than a few fics involving Sunset Shimmer from
- Bitter Tears: An Anon-A-Miss Fic has the Equestria Girls come down with a Heel Realization after being scolded about how they turned their backs on Sunset based on no evidence, and also deals with the fallout of the original culprits by showing what happens to them after they betray the trust of everyone at Canterlot High School.
- Hell and High Water has Rainbow as the only one of the Rainbooms to believe in Sunset's innocence, which has others view her as guilty by association. The duo end up as victims of attempted murder from a group of particularly disgruntled students, but they recover and start a new life attending Crystal Prep and handling new magical incidents alongside the Sirens.
- Last Light is a Dark Fic that starts while Sunset is still being bullied for supposedly being Anon-a-Miss. The bullying is so bad, especially by her former friends, that she ends up Driven to Suicide. The rest of the fic has Dash and the others dealing with the horrific consequences of their bullying.
- In the RWBY/Overwatch crossover fic Reaping with Sorrow Weiss, Yang, and Blake beat Jaune near to death and throw him into a Grimm Pool. Unluckily for them, Jaune comes back with Reaper's powers and a thirst for vengeance.
- Friendship is Failure #10 is a Teen Titans/My Little Pony: Friendship Is Magic crossover that is also a rewrite of The End of Ends (which is under Western Animation). In this story, Beast Boy is "betrayed" by Terra and the rest of the team, the former for breaking up with him in "Things Change" and the latter for supposedly not caring about him. This leads to Beast Boy lashing out at them, and eventually becoming the supervillain Count Logan who wants to end the universe (which includes Equestria) because everyone else is happy while he's miserable. Wait, that sounds oddly familiar...
- The Bolt Chronicles: Narrowly averted in The Blood Brother when Bolt finally realizes how badly he has been treating Mittens and apologizes to her.
- Downplayed in TRON Patchwork Fic "Up and Apart," and told from the point of view of the "betrayer." Jet Bradley and Sam Flynn have worked together on an annual prank on Encom, but after Jet starts working for Encom, he realizes that Sam's pranks aren't having any effect on the Pointy Haired Bosses in charge and more likely to hurt the low-level employees like the security guard who they had to evade to hack the company computers. Jet tells Sam that he won't participate in the pranks anymore and Sam takes it badly, leading to their estrangement.
- A two-pronged rendition in Cabin Fever Fan Fic, Cabin Fever: Parting Shot. Paul feels betrayed by the girl he's pursuing (and who, it's implied, has been leading him on), when he catches her having sex with some other guy after a night of heavy drinking. At the same time, Marcy feels betrayed when her boyfriend, Jeff, acts like "it's no big deal" after his best friend decided to insert himself into their lovemaking and create a threesome, without Marcy's consent. Soon enough, Marcy and Paul come to lean on one another for moral support with their own separate grievances, and eventually become a sexual pairing themselves.
- Dozens if not hundreds of Harry Potter fics involve Harry's friends turning on him and throwing him into Azkaban. Enough so that this plot is mentioned on the series' Fandom Specific Plot page.
- In ''Susan Bones and the Prisoner of Azkaban'', Harry is thrown in Azkaban for Cedric Diggory's murder and only Susan Bones believes he is innocent.
- In Consequence Harry is sent to Azkaban for the murder of Dolores Umbridge, and again no one believes him, not even Hermione and Ron.
- In the aptly named ''The Betrayal of Harry Potter'' Harry is sent to Azkaban after Ron tells the judges Harry used an Unforgivable Curse. Only Hermione sides with Harry and he escapes to kill those that betrayed him, becoming a new Dark Lord.
- In Harry Potter and the Freedom of Apathy Harry is condemned for torturing Bellatrix Lestrange near the end of Order of the Phoenix.
- Percy Jackson itself has a ridiculous amount of these. In most of them, Zeus, Poseidon and most of the big gods betray Percy, Anabeth almost always dumps him and he's left alone. Cue a new darker colder Percy that gets a ridiculous amount of power boosts and a new girlfriend, ranging from other demigods like Thalia and Piper to proper gods like Artemis, Aprodhite etc.
- In The General's Side, Ruby is betrayed by her team, CRDL, and JNPR. The only one not in on the attack was her sister Yang. Afterwards, Ruby joins the military and ends up under Ironwood's wing.
- Henceforward is a RWBY comic where Blake betrays her team and nearly kills Ruby. However, there were reasons behind her sudden FaceHeel Turn.
- In Queen of Grimm, Pyrrha, Weiss, and Team CRDL decide Ruby is too much of a load on them and try to kill her on a mission. Ruby is saved by talking half-Grimm beings, but now wants revenge on her former friends.
- Ruby Rose, Remnant Knight is a betrayal fic where Ruby's team and most of her peers turn on her after she's deemed a traitor for sparing the lives of White Fang members.
- In the DC Super Hero Girls fic Super Villain Prevention 101, Harley Quinn's friends turn on her when they learn about her past actions. This takes a dangerous turn when Supergirl isn't around to save Harley from the Joker.
- My Little Pony: Friendship Is Magic: Rainbow Factory sees Rainbow Dash of My Little Pony: Friendship Is Magic betray Scootaloo by running a factory that mercilessly slaughters ponies, show no remorse for it, and attempt to kill Scootaloo to keep it all running without interruption, all while telling Scootaloo that she never loved her.
- In The End of Ends, Beast Boy is "betrayed" by Terra and the rest of the team, the former for breaking up with him in "Things Change" and the latter for supposedly not caring about him. This leads to Beast Boy lashing out at them, and eventually becoming the supervillain Count Logan who wants to end the universe because everyone else is happy while he's miserable.
- The Rainbow Connection is a Rainbow Brite betrayal fic where Sixth Ranger Stormy turns evil after she feels the Color Kids left her for dead. As an adult, she returns to Rainbow Land and then proceeds to go on a massacre. Unusually, Stormy is the main villain instead of the protagonist. The also now-adult Rainbow Brite must stop her.
- The Season 3 Premiere of Miraculous Ladybug, Chameleon, generated not so much a wave as a tsunami of these kind of fics. Given that a good chunk of the episode involved Lila turning pretty much all of Marienette's friends against her with ridiculous ease, is like the writers were asking the fans for it:
- Marinette Dupain-Cheng's Spite Playlist follows the titular character to a new school after the events of Chameleon, where she proceeds to make new friends. Most of her former classmates are Demoted to Extras, save for Adrien, Chloe, Alya and Lila.
- LadyBugOut begins when Alya betrays Ladybug's trust by posting the photo she took in "Oblivio" to her blog without context, then insists that she's done nothing wrong because Ladybug, as a Super Heroine is a public figure and thus doesn't have any right to privacy or fair representation. Ladybug responds by starting her own blog, ruining the Ladyblog's reputation by exposing her lies... which Alya naturally blames her for.
- Adrien/Chat Noir also betrays Ladybug by putting his personal desires first and foremost, trying to force her to accept his attention while claiming that their matched Miraculouses mean they're meant to be together. This escalates to the point of him losing the Black Cat Ring after an Accidental Public Confession exposes his entitlement to the public.
- The One to Make It Stay has "Chameleon" play out slightly differently, with Rose and the other members of Kitty Section discovering Lila's true nature. As a result, they become Marinette's support network, as she grows closer to the band... and to Luka, leading to her moving past her disappointment with Adrien and dating him instead.
- White Hot Morning in particular has her dealing with Alya and Chat Noir, standing up for herself against their poor behavior and asserting that she deserves better than what she's gotten from either of them.
- All the Laughs We Had in the Past, meanwhile, sees her confronting Chloe over her refusal to change, and the situation with Chat coming to a head when he tries blame her for everything and loses his ring to Miracle Queen.
- Burning Bridges, Building Confidence brings in Marinette's cousin Cole as a much-needed ally after the events of "Chameleon". Marinette goes on to build a new Girl Posse while dealing with Lila, Alya, and their misguided classmates' ongoing harassment.
- to lose someone features Marinette's classmates tearing up her sketchbook on Lila's orders to 'teach her a lesson'. Marinette anticipated this, and turns it around on them by revealing that the sketchbook they just ruined was filled with projects she was working on for their benefit — and no, she has no intention of redoing any of that work. She then spells out for them just how much it would cost to commission her for any of that: far more than any of them could afford.
- In Audacity, Adrien betrays Marinette by taking her earrings and wished for his family (bring Emilie, his mother, back to life) to be whole no matter the cost. His other wish is for Marinette to love him. Since the wish requires an Equivalent Exchange, Marinette's mother is killed in the new timeline. Marinette loves Adrien but for some reason she feels betrayed. Marinette doesn't remember the wishes until she meets a certain Boy Wonder.