Avery Bullock has moments of this, both to Hayley in a brief fling, and later to his cat.
Bullock:[threatening his cat] You think you're better than me? You're not better than me! You're going to learn a hard lesson!
When Hayley Smith gets dumped, things get ugly. Really ugly.
Hayley: I think I'd go maximum crazy! I'd murder Bill... burn down the neighborhood... rape Roger!
Sadira in Disney's Aladdin: The Series is a "street rat" like Aladdin was, and falls for Aladdin the way he did for Jasmine, but, since he's in love with Jasmine he refuses her. Then she stumbles onto an ancient library of forgotten magic, and the end result is increasingly dangerous plots to get rid of Jasmine and take Aladdin for herself, including rewriting reality at one point and altering his mind. Eventually she gets over her crush and befriends the gang, but almost has a brief relapse when she believes they don't trust her.
Mai from Avatar: The Last Airbender is not happy when Zuko, not wanting to drag her into a life of treason, breaks up with her to go join the Avatar. She does end up saving his life and getting thrown in prison for betraying Azula, and they're later reunited. Mai later warns Zuko to never break up with her again.
In The Legend of Korra, several offhand remarks reveal that this trope once applied to ChiefLin Beifong, of all people. When Tenzin left her for Pema, she not only attempted to have Pema arrested, but also caused considerable - though unspecified - damage on Air Temple Island.
Eska for Bolin in season 2. When he leaves during their wedding she chases after him sporting an insane Nightmare Face.
Amora the Enchantress in The Avengers: Earth's Mightiest Heroes! is this to Thor. She takes out her anger from being rejected by him in battle with Thor and his allies frequently. This follows along with her comic book character.
This is part of Mad Hatter's origin in Batman: The Animated Series. He had a crush on his secretary, who actually was named Alice, but she didn't reciprocate. Also, Harleen is in such Mad Love with the Joker that she goes nuts when Batman even suggests that the Joker is just using her and doesn't love her. In response to his statement that the Joker doesn't love her she denies this and tries to kill him in a tearful rage saying that he's in the way. This is also a result of the Joker's obsession with Batman and subsequent rejection of her advances.
Betty Boop: In Boop-Oop-A-Doop Betty is a circus performer who is lusted after by the Ringmaster. At night, the Ringmaster accosts her in her tent and hits on her. She responds in disgust to his inclinations and slaps him. He then threatens and attempts to rape her until Koko the Clown comes in to rescue her.
Lizzie on Codename: Kids Next Door in regards to Numbuh One and King Sandy in regards to Numbuh 3. When Numbuh One repeatedly shows more interest in hanging out with his friends over her she gets him to put on the Boyfriend Helmet that enables her to brainwash him into staying with her. When Numbuh 3 rejects King Sandy he varies between tying her up and threatening to burn her favorite Rainbow Monkey toys in hot nacho cheese to force her to marry him.
Vlad Masters of Danny Phantom doesn't take rejection, whether in a romantic sense or platonic sense well. With Maddie he wants to kill her husband Jack and take his place. With Danny, when he repeatedly rejects his numerous We Can Rule Together offers and wishes to take Jack's place as his father he decides to create a clone of Danny and attempts to murder him.
The Martian Queen in the Duck Dodgers episode "The Queen Is Wild", who seeks revenge on Dodgers for rejecting her in "To Love A Duck". Dodgers, being Dodgers, has completely forgotten the entire incident.
In DuckTales (1987), Gyro invents a robotic maid to help take the strain off Scrooge's housekeepers. His first attempt is so emotionless, it creeps everyone else out. So he dials up the emotions, creating a robo-Yandere who instantly falls in love with Gizmoduck, who unbeknownst to her is just a normal duck in Powered Armor. When he tries to let her down gently by explaining, she interprets it as him having another lover, and literally explodes in a rage.
El Tigre: As the rest of her family in regards to the Riveras, Black Cuervo absolutely refuses to give up romantic interests in Manny after numerous rejections all the while continually trying to destroy him.
Meg goes Yandere sometimes when she gets rejected by a guy, namely Brian. She's arrested for sexual assault when the burglars who have broken into the Griffin house refuse to rape her. In episode "Barely Legal", Meg threatens to kill herself after her date for the dance rejects her and also threatens to kill herself if Brian refuses to go to the dance with her.
Stewie acts like this sometimes as well, most notably in regards to his babysitter LaDawn; he breaks her boyfriend's legs, ties him up and locks him in his trunk leading to his death. Also to Olivia when he was married to her, when he found her with another guy he burned down the house when she and the other guy were still inside.
Also, there's Joan the maid in the episode "I Take Thee Quagmire" who marries Quagmire. When Quagmire tries to bring up divorce following becoming aroused by seeing Lois's breasts Joan goes into Yandere mode and threatens to cut both herself and him with a kitchen knife, right before saying "I love you Glen." When Quagmire says "I love you too insane woman I'm having second thoughts about" Joan goes into Freak Out! mode again and screams "WHAT?!"
James Woods is shown to have a obsession with Peter and its implied he developed feelings for him to the point of acting jealous of Brian. When Peter forgets about a dinner with James that he planned for them he comes home to find James pissed and acting like a stood up date.
There's a scene spoofing Mario where after Mario saves Princess Peach from Bowser he asks her for a kiss. She refuses despite him saving her life and this pisses him off. He then tells Bowser he can have Peach who proceeds to bite off Peach's head.
Peter once offhandedly mentions to Lois that if he comes home one day to find her with another man he'd kill them both. He also acts incredibly violent towards any man Lois shows attraction towards, including punching his own reflection when she said he was handsome.
Quagmire attracts another yandere in the form of Sonja who drugs him to guarantee sex with him and simultaneously beats him up while expressing forceful affection to him. She also kidnaps him in an attempt to make him her boytoy and when Peter and the gang try to stop her she attempts to shoot them.
Peter drives to his boss Angela's house, and discovers her attempting to commit suicide in her garage by inhaling the exhaust from her car. Quickly resuscitating her, Angela confesses that she has no hope in life, after not having been with another man for more than ten years. Deciding to help her out by getting her a date with another man, Peter disguises himself as a high society Englishman named "Reginald Knickerbocker." The two then have dinner together, before Angela brings her date back to the house and tries to seduce him, while still threatening to kill herself if he refuses.
When Peter refuses to have sex with Lois because of her having gained weight she gains even more weight to spite him and secretly desires him to touch her again. Also, when he refused to have sex with her due to taking an abstinence vow she got fed up and jumped him.
Trixie attempts to kill Timmy when he breaks up with her in "Just the Two of Us".
Super Bike, an animated bike, towards Timmy. When Timmy refuses to make Super Bike his permanent bike Super Bike attempts to kill him. "If I can't be your bike...nobody can!"
Berry from the Foster's Home for Imaginary Friends totally fits this trope, acting sweet and kind, but being homicidally jealous of anyone who she perceives as a threat to her relationship with Bloo, which is even more imaginary than she is. She didn't react well when Bloo rejected her and went into a rage.
The Planet Express Ship from Futurama. She tries to kill herself and the rest of the crew after Bender breaks up with her.
Curly coerces Rhonda into a relationship with him in "Curly's Girl" using photos to blackmail her into staying with him. He's also quite heartbroken when she cruelly rejects him.
Lila initially feels "kinda bad" after Arnold rejects her and mopes around (according to Rhonda) which leads the other girls to feel sorry for her.
It's hinted that Helga is very angry and depressed whenever Arnold hints he doesn't like her due to her Tsundere personality, and is willing to go to such lengths as threatening to strangle Lila, stalking Arnold and sabotaging Arnold's dates, as well as scaring the girls who had gotten picked to play Juliet so they would back out all out of love for Arnold.
Arnold takes Lila's rejections of him close to heart, making for a Tear Jerker each time.
Lila becomes this in an episode depicting the future towards Arnold when she is shown pining over him to a desperate degree after he and Helga are married, even after he rejects her. She ends up disguising herself as a villain, kidnapping Arnold, and trying to kill/beat up Helga. Of course, this was in Helga's fantasy, so it might not actually happen.
Olga breaks down crying hysterically after her fiance dumps her in a letter.
Heloise on Jimmy Two-Shoes. Among the things she's done when Jimmy hasn't noticed her is doing a "Freaky Friday" Flip on Beezy and Cerbee and fusing Jimmy and Beezy together. There's also "Best Bud Battle", where Heloise chains Jimmy up to keep him from leaving her and locks him in a tiny cage. She also goes into a homicidal rage sometimes when Jimmy shows more attention to his Heterosexual Life-Partner Beezy over her.
Lola Bunny and Bugs Bunny both fall under this category in an Season 2 episode of The Looney Tunes Show. They mistakenly believe that the other broke up with them. Lola becomes a monk and takes a year-long vow of silence, while Bugs leaves everything behind and becomes a fisherman. They work things out, though.
Cookie BaBoom, Mayor Tilton's ex-girlfriend on The Mask episode "Flight as a Feather." Uses a variant of the Stock Phrase, "If I can't have you, then no one can" (on the episode, it was, "If I can't have Mortimer, then no one can!" Standard. Is still bitter over being dumped by Mayor Tilton? Okay. Uses two strategically placed explosive belts strapped around her body to kill herself, the mayor, and everyone else around her because of the deep-seated resentment she has over being dumped.
In "Plane Crazy" Mickey Mouse gets angry when Minnie rejects him when they're in a plane together and deliberately flies so that she falls out of the plane. When he again tries to kiss her she refuses him again and he angrily forces kisses on her.
Little Acorn in "Puppet Bride" of My Life as a Teenage Robot tries to force Jenny into marrying him even though she refuses him and before that ties her up after having some puppets beat her unconscious.
Pinkie Pie also has a mental breakdown when she thinks her friends don't like her parties and don't want to be her friends anymore in "Party of One", complete with her temporarily talking to inanimate objects and sporting a Slasher Smile.
Twilight Sparkle has a freak out in "Feeling Pinkie Keen" when her normal approach of methodical research doesn't yield an answer to how Pinkie Pie can apparently predict the future with "Pinkie Sense". Essentially, it's the universe rejecting her entire life's philosophy that nothing is unexplainable by giving her something that is that drives her batty.
In "Daring Don't", the adventurer Daring Do refused to let Dr. Caballeron team up with her in one of her books, leading to the two becoming bitter enemies.
In the Pepé Le Pew short "Really Scent" Pepé removes his odor by locking himself in a deodorant plant so Penelope (Or known as "Fabrette", in this instance a black cat with an unfortunate birthmark and thus an arguably different character) would no longer be afraid of him. However, Penelope had decided to make her odor match her appearance and had locked herself in a Limburger cheese factory. Now more forceful and demanding, Penelope quickly corners the terrified Pepé, who, after smelling her new stench, wants nothing more than to escape the amorous female cat. Unfortunately, she will not take "no" for an answer, gets an angry look on her face when Pepe repulses her advances and proceeds to chase Pepé off into the distance, with no intention of letting him escape.
Gerald in Perfect Hair Forever. He starts as a relatively "normal" character, but come the April Fool's final episode, he's revealed to have a crush on Brenda (despite her cutting off his ear at the beginning of the series — it's that kind of show) and starts going crazy over the fact that Young Man is going to marry her. He attempts to use some hamburger necklace thing to mind-control Brenda to love him, and when that fails, he tries sniping Young Man at the altar outright. The show cuts to black before the results are shown, it's not completely revealed if he killed him or not.
Dr. Doofenshmirtz from Phineas and Ferb was this in an episode. The outcome of his Evil Plan depended on whether or not his date went well, because (as he admitted) he can't handle rejection well.
The Problem Solverz: Katrina Rad is obsessed with Roba and stalks him in "Magic Clock". She then steals a time-freezing clock so the two of them can be together for eternity and tries to marry him against his will. When Roba refuses to kiss her at their wedding, she threatens to rip a hole in the fabric of the space-time continuum.
An episode of Regular Show has Starla, Muscle Man's old girlfriend. She falls in love with Mordecai, and he starts dating her just so he can get her and Muscle Man back together. But when Mordecai can't take it anymore and breaks up with her... well...
Depending on the Writer, for all his Jerkassness Ren gets quite depressed to a pathological degree whenever Stimpy shows signs of wanting to leave him, pushes him away, or shows interest in someone or something (in this case a chicken) that's not him.
"Double Header" had a particularly heartbreaking scene that is very reminiscent of a couple breaking up. Ren is trying to send Stimpy away, but when Stimpy realizes this, he pleads him not to. Ren is sick of his antics and tells him to get lost, while Stimpy continues begging Ren to take him back.
Ren: Well, I just don't like you.
Stimpy: BUT I LOVE YOU! Please, please take me back! Please...
There are two separate occasions of Patrick acting like a Yandereto Spongebob. When Spongebob's gift is late getting to Patrick he assumes this means that Spongebob didn't get him anything and eventually goes on a mad rampage. Another time when Spongebob gives up his old life and friends to live a life among the jellyfish Patrick chases him with a jellyfish net telling him "If I can't have you as a friend I'm gonna make you a trophy!"
Another time when Gary chooses to be Spongebob's pet again after getting a cookie Patrick had in his pocket Patrick is upset and screams at Gary "Gary, I thought what we had was SPECIAL!!!!!!"
Kitten. "Nobody dumps Kitten! You're going to pay for this Robbie-poo! YOU'RE GOING TO PAY!!!!!"
Raven falling in love with Malchior, who lived in a book in the episode "Spellbound". However he turned out to be a Mailer Daemon, who then proceeded to trick her into releasing him from the book. While Raven was heartbroken, she did get revenge during a final fight after he said "I got what I wanted and I don't need you anymore" and put him back in the book using the techniques that he taught her.
When Terra reveals to Beast Boy how she was working for Slade she begs him to say that despite that he'll still be her friend. Beast Boy says coldly "Slade was right, you don't have any friends." In response she gets a horrified look on her face before retreating into the shadows and putting on a expression made of Tranquil Fury. She later punches him in the face when pulling a FaceHeel Turn and swearing revenge on him and the other Titans before trying to kill him.
Elmyra has a cute crush on Max and one short called "Can't Buy Me Love" has Elmyra meet an evil little girl called Rhoda. Elmyra sees hearts and positively MELTS when Rhoda says she'll let her be her best friend, and spends the rest of the picture bending over backwards to make Rhoda like her. It plays VERY much like any episode where Elmyra chases Max, only way more seriously, and heck, Elmyra even lets Rhoda HAVE Max (who doesn't want him after mere moments). And after she learns her lesson about not needing to give someone something so they'll like you, Rhoda comes by her window and says she'll be her friend again if Elmyra steals her mom's car keys and drives her to Utah. Instantly Elmyra says "okay" and rushes off eagerly to Rhoda's side. So not only is Elmyra completely infatuated with Rhoda, but apparently Rhoda can't leave Elmyra alone for five minutes, even after Elmyra dumped her. Elmyra also had a thing for chasing Fifi around, a voluptuous female skunk which persisted even after Fifi skunked her and had Elmyra go as far as to pose as Fifi's crush Pepe le Pew. Its notable that during all these times she shows affection towards the above respective characters and they rebuff her she falls to pieces and cries.
When Max tries to get with Mitzi she rejects him in much the same manner that he did to Elmyra and chooses Dizzy instead. Max shows a rare moment of regret and sadness.
In "Flea For Your Life" Itchy a young flea girl stumbles onto a corrupt business man's evil plan. When she attempts to tell the madman she plans to reveal his scheme he promptly has her apprehended and silenced... then forces her into wed-lock by threatening her family when she refuses to marry him.
In the Tom and Jerry cartoon "Blue Cat Blues", Tom is sitting on a railroad track, waiting to be run over, after his girlfriend leaves him for another. At the end, Jerry joins him after his own girlfriend does the same.
Total Drama: Dave's crush on Sky started off as a normal teen crush, but by episode 3 he started becoming more of stalker, and then devolved into a complete Entitled Bastard acting just because likes Sky and Sky admitted to liking him he should be her girlfriend no matter how clear she makes it she doesn't even when she rejects him. It gets even worse when he sacrifices the game due to her rejection and acts like he deserves her even more because "he sacrificed himself for her" when really he quit because he didn't wanna be there if Sky rejected him.
In "Matchmaker" the villain Eugene is bitter for being rejected by a girl on Valentine's day so he hatches a plan where he uses a device to disguise himself as the ideal boyfriend for the female's at Beverly High School. He plans to make them fall in love with him and then dump them at the Valentine's day dance in order to get revenge on all women. However, Clover stops him before he can dump the girls and reveals his ruse.
In "Zero to Hero" after Alex dumps him following a disastrous date, Virgil ingests the villain's Super Serum and repeatedly puts her life in danger so he can save her from disasters he caused. She continues to turn him down, so he drinks the last of the serum and moves on to trying to beat her to a pulp. To be fair, he wasn't quite himself due to the 'roid rage-like effects of the serum.