Crossover
- Infinity Crisis: Sinthea Schmidt, granddaughter of the Red Skull, made her first kill when she was seven.
- Princess Jody from Super Milestone Wars
, subverted since she's older then she looks: she's actually over 1000 years old - Lila from Raise Your Voice Against Liars. Starting at 11 years old she has caused 6 former classmates to commit suicide by manipulating the rest of her class into bullying one student, moving away with her diplomat mother, switching schools and finding a new victim. She almost manages a repeat with Marinette, if not for Luka's intervention and her eventual change of heart at the hands of the Phantom Thieves.
- A Clash Of Neets: Komekko Stark might seem, at first glances, like a fairly normal little girl with an abnormally massive appetite, who spends her time either eating, trailing after her big sisters, or playing with her imaginary friend, Vanir. Make no mistake, however: beneath that exterior is a born manipulator, natural blackmailer... and Kid with the Leash to the not-so-imaginary Demon Lord Vanir.
- Massive Multiplayer Crossover With Pearl and Ruby Glowing features many instances of Troubling Unchildlike Behavior from trauma victims, but only two stand out as true spawns of evil. Darla Dimple became a Self-Made Orphan some years prior to her current age of eight, and frames Danny for raping her, going so far as to injure herself with a hairbrush handle to make it look real, while Megan Parker has murdered several other local children and framed her brothers by stealing semen from used tissues in their wastebasket to plant on the bodies. Flutterina, here a real person rather than Double Trouble's persona, is a strong runner-up, manipulating her cousin Glimmer into making an easily disproved False Rape Accusation and becoming a pariah for lying, the lie being indirectly responsible for Peekablue's near-murder and subsequent agoraphobia.
- In a Chaosverse Omake in Chaos Effect we are introduced to Daemon Pickles, a Chaos who finds himself trapped as a 6 month old in the world of Rugrats. Daemon uses the Omake to explain to a terrified Dil how he's going to render him mute and then force him to watch as he brutally murders all the other babies and pin the crimes on the parents so they all go to jail. The Character Reveal Title Card reveals he is the most EVIL Chaos in the entire Multiverse.
- Word of God has stated that Daemon escapes into the multiverse after using the Rugrats' natural chaotic energy and havoc causing nature... to set off every nuclear device on his planet, killing everyone while he happily escapes to murder more.
- Alyssa Storm from Ask The New Hope's Peak. Her very first appearance has her kill her grandmother by using a sonic weapon that causes her victim to bleed out from every orifice in their body.
- Forward: The resident psychopathic child is a mind-controlling girl created by the Academy. Impulsive and irrational, she goes on violent rampages whenever she thinks she's encountered someone connected to her torture. This ultimately leads to both the Hands of Blue and the crew of Serenity tracking her down by essentially following the trail of corpses.
- Anna is shown to be this in a parody of "Do You Want to Build a Snowman?" called "Will You Help Me Hide a Body?" At the beginning of the song, she asks her sister Elsa to help her hide someone's body "before he can decay" singing that "it doesn't have to be in one piece". She's five years old at that point. Her singing about throwing someone down a well, digging up graves and running out of space to hide bodies in caves when she's nine shows that she doesn't get better.
- In the Frozen fic In Pain And Blood, Elsa's youngest son Aksel hates his older brother and wishes he was heir instead. At age eight he uses his ice powers to try and seriously injure his brother. He's completely unrepentant about it and considers it Aron's fault for being "weak". A decade later, Aksel tries to poison Aron and almost gets away with it, but he's found out before he can murder his brother.
- In Neither a Bird nor a Plane, it's Deku! (DC Comics & My Hero Academia): Hisashi brings up the trope while trying to dissuade his wife Inko from adopting an alien baby they found while camping at the base of Mt. Fuji.Inko: So what if he's an alien? It's not like all aliens are evil. The Martian Manhunter certainly wasn't evil. Besides, he's just a baby, and babies can't hurt people.
Hisashi: Yeah, but the people they grow up to be can! Besides, how do we even know he's even actually a baby? [steps over to Inko and peers at the baby] For all we know, he comes from a planet of beings that just look like babies, and they all try to use their overwhelming cuteness to infiltrate societies and destroy them from the inside! [baby giggles and squeezes Hisashi's nose] That doesn't disprove the theory. [removes baby's hand from his nose]
- Abraxas (Hrodvitnon): The Zmeyevich in Apex Cybernetics' custody apparently bit a security officer badly enough that said officer needed to seek a hospital's medical attention.
- Both Charlotte and Vendetta in Paint It Green, Blue, Black, but especially Charlotte after she awakens the Repressed Memories of her parents' murder. Charlotte goes on tangents about people having "jam" inside them and how she wants to spread it everywhere. She even weirds out Vendetta.
- Scootaloo in Ask Pinkamina Diane Pie is an accomplice of the Serial Killer protagonist.
- In Ultra Fast Pony, Apple Bloom is the preteen child of a mob family, and she's already taken to the lifestyle: blackmailing adults to get her way and burning down schoolhouses. Her friend Sweetie Belle is a creature of id, who destroys stuff on random whims and expects she can charm her way out of the consequences.
- The Ships Ahoy! universe of fanfics portrays Odd Todd as one of these, just like in canon. What he does in the stories and what he does in canon — preferring to create oddness rather than eliminate it, getting fired, and getting revenge by launching a pienado attack that injured many — is almost the same.
- OSMU: Fanfiction Friction has Basil Valentine note , who wants to get in touch with Todd (portrayed here in his Reformed, but Not Tamed state) in order to learn the secret of Odd Squad's Proportional Aging so he can stop himself from aging backwards and eventually disappearing. He has two henchwomen, Ambrosia and Nectar, and also has skillful Psychic Powers which he uses to torment Todd.
- Pokémon Reset Bloodlines:
- Sabrina is revealed to be one in her side story, as she started using her powers to terrorize her hometown when she grew sick of their lazy attitude.
- Ash's father is, if anything, worse than that: he killed his mother at the age of 10, and only got worse from there.
- Rory Ryan of Ask the Ryans can be just as nasty as big brother Aran, often playing cruel jokes on the other boxers and trying to get her brother to load his gloves with firecrackers.
- RWBY: Scars: Even as a child, Neo was aggressive. She stabbed a girl at her daycare with a fork and threw rocks at squirrels. Neo's behavior caused her mother to reject her as a "monster".
- Oblivion: Medusa was this as a child. As seen in her younger sister Shaula's flashbacks, she mercilessly mocked Shaula for every failure, convinced her that their father's lesson on survival of the fittest meant that as the weakest sibling, she was going to die, and was, in general, a cruel Big Sister Bully. Her response to their parents' murder was to restrain Shaula with her Vectors, taunt her about how Shaula couldn't go to anyone for help anymore, and then attack her with a knife. It's specifically stated that she did that when she was twelve years old.
- As an adult, when she's about to physically rip out Shaula's soul, Medusa mentions that there were numerous times during their childhood when Shaula must have thought that she (Medusa) was really going to kill her, implying that she attacked her younger sister like this on a regular basis.
- In An Ideal Gift, Donatello claims that while the four-year old Irrilia is usually adorable, she can be "crazy-scary" when angered, a trait he insinuates she got from Raphael.Raphael: Trust me, my temper's got nothin' on hers.
Unsorted
- Arial Kuyumaya of Rosario Vampire: Brightest Darkness is a downplayed example. She's a cute little snow girl... with a Hair-Trigger Temper that borders on Ax-Crazy and a penchant for extreme violence when provoked. At least once, Moka and the others have pondered how Arial was accepted into Heaven in the first place, and Mizore has outright called her a "fucking nightmare." That being said, it's noted she is in fact a good soul, and she's not without her Pet the Dog moments.
- Brox in With Strings Attached was an elven woman of unknown age who was murdered and then reborn as a five-year-old boy. Given her taste for sadistic jokes (that's why she was murdered), considerable knowledge, and willingness to step on people to get what she wants, she qualifies.
- In Attack of Giygas, we have Porky and Ashley. Ashley ends up turning Lucas into one.
- My Little Wesker expands on Wesker's history quite a bit. He was an advocate of eugenics and Blue-and-Orange Morality at an early age, and at thirteen years, Wesker successfully pulled off the murder of a 16-year-old bully after he decided he was a threat to his continued development.
- In the Gensokyo 20XX Series, Yukari was this is as a child, along with being a Child Prodigy, being able to manipulate other youkai before she was out of babyhood (she was three when she started) and often manipulated them into attacking villages and playing the Wounded Gazelle Gambit.
- In The Tantrum Phase and its sequel, we have this with Chen. a rather tame example, who, in the former, throws tantrums and behaves horribly, even causing Ran and Yukari injury, and, then, in the latter, she tricks Marisa and both make trouble for Ran.
- In 20XXV, Reimu seems to be one to a lesser degree seeing that she once made it a habit to trick someone into sticking something in an electric socket, apparently, for her amusement. Of course, there is the fact that Baka is pointed out to be Too Dumb to Live, seeing as he kept falling for it, along with the fact that he did use to pick on her.
- In ongoing The Legend of Korra darkfic Crescendo, the sadistically imaginative serial killer for whom the whole city has been on the hunt turns out to be a twelve-year-old boy who's been lurking in plain sight from the beginning.
