Aryan Nation, a white supremacist "superhero" from the Global Guardians PBEM Universe, admits that the reason he took to crimefighting was to repudiate the abuse his trailer-trash, redneck father heaped upon him while growing up, and is actually proud of the fact that he's not "some drunken Klansman in a bedsheet burning crosses", despite still being a racist Jerkass. The fact that he's doing the very same thing to his own kids that his father did to him hasn't occurred to Aryan Nation yet.
Fairly common as a backstory for characters in Survival of the Fittest, in that there are at least several examples per version. It was particularly common in v1 and v2, and while it isn't as common in later versions they still pop up. V2's Mariavel Varella is one such example, having been abused physically (and in a retconned thread, sexually) by her father, who also killed her brother.
Elsdon's father in The Eternal Dungeon series for no apparent reason at first and then in a strange, backfired attempt to "fix" Elsdon of his own sadism. Elsdon is understandably self-hating and mostly Ax-Crazy at the beginning of the series until he's given a chance to channel his own desires productively.
MSF High Forum: Destiny's mom wanted to possess her daughter to avoid growing old and dying, she killed destiny's father to do this followed by being killed herself along with Destiny. And that's not getting into Casey'sfolks ....
In Touhou: a Glimmer of an Outside World, Marisa's father. Amongst other things, he threw her out—despite Marisa's being sixteen or seventeen at the most — and hit her when she tried to get back in.
Generator's dad. Physically and emotionally abusive, especially after Generator's mother was killed (which may have been dad's fault). Generator would have been beaten to death if she hadn't manifested her mutant power right then. Money? All gone now that dad's on the run from the police for other crimes. The only reason dad didn't rape her is probably because she wasn't a girl back when she was living with her father.
Circuit Breaker as well — parental abuse doesn't get much worse than murdering your oldest child in front of the other two, then burying the body under a church pulpit and forcing everyone to pretend that the he never existed.
Ask That Guy and the Nostalgia Critic; Ask That Guy seems to think that he was never good enough and they told him that he would have go to back in the dumpster where they found him, while the Critic portrayed them as monsters ripping him apart in a kindergarten drawing. And Ask That Guy's response to "Why does Daddy hit Mommy?" and the Critic apparently hiding in the cupboard when he was scared seem pretty suspect, as are Critic's rants on dreams not coming true and parents putting pressure on their kids. Also, with Critic being a weepy Psychopathic Manchild and Ask That Guy having twisted views on sex and women, it was pretty obvious from the start.
Also treated for laughs was the The Nostalgia Chick's childhood. Her mother made her feel inadequate, her uncle sexually abused her and her father never gave her any love. Word Of Lindsay is that she retreated into always watching television to escape her parents yelling.
Played for Drama in Demo Reel, where Tacoma's family abuses him for sending his father to jail, Rebecca's parents make her feel worthless for not knowing what she wants to do with her life, and Donnie's family actually want him to be alone while they spend holidays with his wife.
Critic's show introduced Uncle Lies, an Ask That Guy-like sweater-wearing father who loves traumatizing his children, and Aunt Despair, a miserable drugged out smoker mother who neglects her kids. Later on he connected Hyper as their oldest daughter, providing her with a Freudian Excuse for the way she acts.
The titular character's father in Dragomirs Diary is almost unreasoningly abusive and berating to his son, for no reason that Dragomir himself can muddle out. Oswald the Farmer is such a horrible dad that he essentially calls Dragomir a quitter after Dragomir is revealed to have died and been brought back to life.
None Too Holy has the Pijavica, who is actually Aleksander's mother who raped him multiple times as a child.
Under The Cold Moon has Siegfried Gunmarsohn, who raised hundreds of werewolves solely to use them as cannon fodder, and would frequently abusive them when they were alive. Even when his competent daughter, Sieglinde Nomura, dies towards the end of the story, he just murmurs "oh fucking well" to himself and shrugs it off.
Smirvlak's Stone has Gnekvizz's parents, both of whom were verbally (sometimes physically) abusive to him due to his homosexuality.
Scrambled Egg has Snorrv's father, who physically abused him for years and later molested him just to determine how fertile he was.
Godzilla himself was portrayed as one in the earlier seasons of Monster Island Buddies, being quite neglectful toward Minilla and downright hateful toward Zilla. It's later revealed that the cause for this misbehavior was that his own father, the original 1954 Gojira, was rather rude toward him and outright consisedered him "the worst accident ever".However, after seeing Minilla scaring away Monster X/Keizer Ghidorah's army with a giant robot he built by himself, Godzilla has a change of heart and now aims to become a better parent. King Ghidorah is also shown to have issues with his own father, Monster X/Keizer Ghidorah, who in turn also has daddy issues with Grand King Ghidorah, his dad, who behaves pretty much like Abe Simpson with his son.
Bowser is usually a terrible parent to his son, Junior. One example would be when, after Junior fails a test, Bowser beats him with a cable cord. Oddly, though, Bowser seems to change between being kind to his son and being an abusive Jerkass.
Charleyyy once threw his infant daughter down a staircase. note It's just a baby doll, but still.
In the "Bowser Jr's Playtime" videos, Bowser Jr. plays a man named "Jr." (his wife played by Joseph and his daughter played by Cody), and "Jr." is an abusive workaholic who apparently sleeps with his secretary, calls his wife a whore, and beats his wife and daughter, constantly berating the both of them. Scary when one thinks this is just play-house, and most kids base such things on their home life.
Downplayed with Mario. After he reluctantly became the Parental Substitute to Jeffy, he tried to get rid of him in "Jeffy's Special Easter!" and "Where's Jeffy?", shot him with a Nerf gun saying, "Die Jeffy!", in "Bowser Junior's Nerf War!", and locked him in the bathroom and pretended not to hear him in "Jeffy's Cellphone!". Though otherwise, he doesn't physically or emotionally abuse Jeffy anyway outside of those examples.
Jeffy's mother Nancy, to the point the poor child is afraid of her. In fact, the only reason she came back for him is so she can get rich, as Jeffy's father Jacques Pierre François left all of his money to Jeffy following his suicide, which Jeffy can get once he turns 18. Hell, she tells Jeffy he can't eat for a week, saying he's hungry!
In a one-off gag, MJTR of Analog Control claimed his father abused and neglected him in the hopes of making him a champion at Sportsball. This turns him into a "Well Done, Son!" Guy for the remainder of the episode.
At his absolute worst, Jeffery Sr. From McJuggerNuggets borders on this. While he's never shown physically harming Jesse, he causes him more than enough grief by breaking his stuff. However, since The Reveal that the series was fake all along, we've realized that Jeffery Sr. is a nice person in real life.
In the various GoAnimate "Grounded" videos, the parents are usually this, depending on the creator. Boris (A.K.A. Boris The Teeth Guy), Caillou's father, is the biggest example of this as he will joyously attack Caillou at times for his punishments, even going so far as to kill him.
Petscop: Once things go dark, this appears to be a Central Theme. This is best shown with Marvin, as, from what we get in the in-game notes, he's done some harm to Care and Micheal, the latter (who might not be his kid) implied to be completely broken, being pleased for some reason that the former isn't growing eyebrows, and the fact that, in Ep. 11, he kidnaps Care after a divorce.
Eric's father was mentioned as being abusive during his childhood, to both him and his sister. He outright refused to speak with Eric when he'd moved to Hollywood to pursue his acting career.
In "This Video Will Take You To Hell", we learn about a child whose parents kept them locked in a room with a mattress, a broken TV, a litter box, and pet bowls. This child turned out to be Sam himself.
My Dad's Tapes: Because of his hatred for women, Chris's father had threatened to start beating his sister. This is what lead their mother to split from him.
Poor parenting is abound in the Science Fantasy world of Magik Online with such parents such as Henry Powells who was a horrible father and it's not hard to see how Maggie and Jack ended up the way they did under his care. Next up is Blackcinders who is a perfectionist stage mom who openly looks down on her son, Smokefang, for never meeting her absurd standards and refuses to let him heal his blinded eye as a form of discipline, and Blackcinders own POV reveals that her parents weren't much better, indoctrinating her with their toxic ideals of strength and ruthlessness starting the cycle with her own children.
Tribe Twelve: Mary Asher is nicknamed "The Selfish" for a reason. Her attitude extended even to her treatment of her son, Milo, who she neglected, exposed to her dating several men he didn't like, and who she used for her own goals, bringing him to her Cult and forcing him to take pills that turned him into an obedient son, who didn't question her weird actions or the presence of Slender-Man.