Galilee by Clive Barker plays it in full where the Barbarossa are concerned. Maddox didn't leave the house for about a century. Luman is so far gone he spent years in asylums and lives now next to the house, secluded for everyone's safety. Galilee is plagued by guilt to the point of avoiding solid land as much as possible, Marietta is a nymphomanic who forgets that the house gets her lovers mad and Zabrina is an overweight alchemist with a serious eating disorder.
Acheri, from Hell's Children, by Andrew Boland, is a creepy child who, despite having no eyes in her eye sockets, can still see you. And that’s just the tip of the iceberg.
Thomas Hardy's Jude the Obscure, in which the title character has a son so weird they don't seem to bother naming him, calling him "Little Father Time", due to being old beyond his years. He goes on to murder his step-siblings and then commit suicide because he believes that they and he are dragging Jude and Sue (first cousins, if the family wasn't odd enough) into even direr poverty, making him a damn sight less self-centered than most kids.
Alia in Dune, born with the knowledge and cunning of generations of Bene Gesserit ancestors. She was extremely creepy in David Lynch's film, very creepy in the Sci-Fi Channel adaptation, and only slightly less eerie in the original book.
Alia is also notable for being one of the few instances where we get to see what happens when the Creepy Child goes through puberty and then grows up. Needless to say, it turns out quite tragic.
In the David Lynch film, she was played by Alicia Roanne Witt, who had received a considerable amount of media attention at the age of three for her 200+ IQ.
Tom Riddle is shown to have been a Creepy Child in a Flashback. At the age of eleven he says to Dumbledore: "I can make bad things happen to people who annoy me. I can make them hurt if I want to." Apparently he also killed a fellow orphan's pet rabbit and hung it up where the boy would find it. The orphanage was not presumably a nice place to be—tight budget, overcrowding, lack of emotional nourishment or adult support of any kind—but doesn't seem to have been an Orphanage of Fear except for persons Riddle selected for his retribution.
Severus Snape had some decidedly creepy tendencies as a child: Watching other kids play from behind bushes (whether or not it was the beginning of a friendship, it's still Paranoia Fuel), and reportedly knowing more Dark curses at eleven years old than most of the seventh-years at Hogwarts. His personality as an adult is kind of like the grown-up version of this trope.
The classic representative of this trope: Rhoda Penmark of The Bad Seed.
Jonathan Lethem's novel Gun, with Occasional Music, features "babyheads", toddlers who have been genetically modified to possess adult-level intelligence. Unfortunately, they also have adult-level cynicism and bad habits.
Pet Sematary. Ye gods. Because normal creepy kids aren't enough for Stephen King, they have to be psycho zombie creepy kids.
H.P. Lovecraft's novella The Dunwich Horror involves a creepy child who appears to grow supernaturally quickly. By twelve, he is approximately seven feet tall, is badly in need of a shave, and has completely adult proportions. This is nothing compared to his brother.
Not a kid, but there's Psychopathic Manchild Jonathan Teatime from Hogfather. In the TV adaptation, he's very Wonka-ish, which only makes it worse. He's been like that since childhood, with the suggestion that as a child he may have murdered his parents, or at least watched them die. Even at the Assassin's Guild, kids know to keep away from people that freaky, a remark that becomes important in the climax.
Lord Downey is quoted as saying that when Teatime was taken in, "We took pity on him because he was an orphan. I think, in retrospect, we should have wondered a bit more about that."
Overlapping with Tyke-Bomb is Coin from Sourcery, who quite calmly converts people into piles of ash or clouds of smoke without seeming to grasp that they're even dead. Is anything bad happening to him? Although Coin is spurred on and encouraged in this behavior by his Wizard's staff, which contains the soul of his insane father. Once freed from the staff's influence, he's a normal boy. (Or as normal as someone who can remake his local reality on a whim can be.)
Not all of it was his father's influence either. At the beginning of the book he creeped out the Grim Reaper.
Also, in Soul Music, we see that Susan very seriously freaked out her principal. Which is very understandable.
She's still at it later in life, although she's mostly learned to control it for her own ends.
Starting in Eldest, Inheritance Cycle has Elva. As a result of his "blessing", Eragon causes a one-year-old infant to mutate into a six-year-old who speaks with the voice of a world-weary adult and has Purple Eyes, becoming the empathic Elva. The other characters get really, really creeped out just hearing her speak.
Artemis Fowl, from the series of the same name, is the world's greatest criminal mastermind and 12 years old.
Also one of the few examples of a Creepy Child protagonist.
Literary/film example: the Stephen King short story "Children of the Corn" is based around a Town with a Dark Secret in which a bunch of creepy children have killed all of the adults, and sacrifice everyone to a vaguely Jesus-like entity called "He Who Walks Behind The Rows" when they turn nineteen.
In the postmodern novel House of Leaves, the character Will Navidson has two children named Chad and Daisy. As events in the book become more and more surreal, the children begin to act quite differently from their normal behavior, at several points becoming the Creepy Child.
A. N. Wilson's A Jealous Ghost contains two children, brother and sister, who are strangely shifty and reserved with the nanny. They like to sit quietly in their room after dinner. Said nanny begins to believe they are being corrupted by their mother's ghost: however, she is very much alive. Oh, and the nanny goes completely bonkers.
Ivy (aka The Archive) from The Dresden Files is a seven-year-old girl containing the entirety of human knowledge and understanding. She talks very calmly about matters of magic and vampires and stuff, and then completely upends the trope and reverts to normalcy somewhat when Dresden's cat Mister walks in. "Kitty!" As Kincaid, the hardened mercenary and a hundreds-of-years-old half-demon known as the Hound of Hell, who used to work for Dracula's father (who is described as the scion of a demon) put it, "Okay, that's just creepy". Dresden refers to her as "the scariest little girl on God's green earth."
The Age of Misrule features the Big Bad, Balor, at the end of book 3. He destroys whole pantheons... and he appears in the form of a Victorian private school boy. And then his face folds back so he can fire lasers at the heroes.
The Dexter novel Dexter in the Dark features his soon-to-be stepchildren Astor and Cody, who are definitely creepy and heading into Psychopathic Manchild territory (Astor being female doesn't seem to rule it out in her case.) No indication that Astor and Cody have been sent into creepy territory by their abusive dad has shown up in the TV series, though, and since the show diverted from the books starting with Season 2, it's no guarantee that the plot will show up there.
According to The Areas of My Expertise, The Virtuous Child is a creepy one parodying Puritanical values. See the page on Glurge. There's also the child prodigies.
Basically, it comes down to this: Child prodigies are fine, but you could do without the violins. If you have ever been alone at night in Penn Station, barefoot, with only a sword cane and a half-empty bottle of brandy, and suddenly, swiftly, with ninja-like stealth, a group of child prodigies surrounds you, rattling their violin cases, you will know what we're talking about.
Angel of Maximum Ride is an angelic-looking child...except that she possesses psychic powers that she canand willuse onanybody. A slightly less creepy example is in The Angel Experiment when she "asks" a woman to buy an overpriced stuffed bear for her, but by Saving The World And Other Extreme Sports she has taken a level in badass and mentally commands all the mutants at Itex to kill the evil doctors. Scary stuff indeed.
There's also the original Jerome Bixby short story "It's a Good Life", basis of the Twilight Zone episode described below. If anything, this version of Anthony is even creepier.
Twins Jane and Alec from the Twilight series. Jane can make people writhe from extreme agony, and Alec can make people feel absolutely nothing. Every other vampire that knows about them is at least slightly scared by them (except Aro). Despite their childish appearance, they're both several hundred years old.
Jane is played by Dakota Fanning (who is decidedly less creepy now that she's mini-Gwyneth Paltrow)
The main character, Will Stanton, from The Dark Is Rising, in his aspect as an Old One. The rest of the time he seems like a perfectly normal boy.
Spider Robinson probably did not intendJake Stonebender's supersupergenius daughter Erin to be a Creepy Child. But I defy you not to be creeped out, or at least Squicked, when at the age of fourteen MONTHS she responds to a compliment with "Why, Uncle Nicky, what a sweet thing to say! I'm going to start fucking when I'm sixteen, would you like to take a number? I can work you into the single digits if you hurry."
The "nudnik" (human, in mouse slang) child in House of Tribes captures mice and other small animals to dissect, and feeds the remains to his pet mouse. Even from the point of view of a human, this is Squicky, and from the point of view of the mouse main character it's positively horrifying.
The title character of Ray Bradbury's short story The Small Assassin — who is a baby.
Avoided in Good Omens: Adam Young, despite being the Antichrist, is a thoroughly normal child due to the lack of any angelic or demonic influence in his upbringing.
Miles and Flora in Henry James' The Turn of the Screw. First, they look very cute and innocent... later, not so much. The story very much relies on readers' interpretation of the event and the narrator. In both variants they come off as creepy. Either they are unusually, disturbingly well-behaved and non-childlike, or they are corrupted by wicked servants and downright possessed by the evil.
Henry/Emperor Kirwan of Draco, the wonderfully creepy hero of an all-but-forgotten short story called Child's Play, by Mary-Alice Schnirring. 20 years before D&D existed, Schnirring came up with the idea of kids organizing and playing about an ancient empire and its adventures and vicissitudes entirely on paper. Turns out the kingdom really exists, as does the horrifyingly undescribed monster in the swamp. Bye-bye, obnoxious cousin Charlie! Glug, glug....
While we're at it, Jane Rice's Idol of the Flies, a classic about a sweet-faced kid who, let's see... killed his parents, making it look like an accident, nearly does the same to his aunt, and tortures animals, among other things, many of which involve lots and lots of flies.
Rosamond from the Nate The Great series — she is not malevolent, but with her gothy appearance and her six black cats, she is extremely strange. Also her spiritual successor, product mascot Emily the Strange.
Colonel Aureliano Buendía was one of these as a child. When his mom Ursula was pregnant with him, he cried in her womb. When he was born, he didn't cry and only stared at the ceiling. As a three year old, he told Ursula that a jar placed in the middle of a table would fall, and it moved to a side until it fell...
While the future Colonel mostly grew out of this when he grew up, his stepsister Rebecca was this when she arrived to the Buendía household at age nine. She would just blankly stare at everyone, suck on her thumb all day long, and eat nothing but dirt... She also grew out of it with age but not before she accidentally spread the "sleep illness" (which caused her odd behavior) through all of Macondo.
One of the 17 Aurelianos note the 17 illegitimate sons of the aforementioned Colonel, all named after him also was like this. He was a girly-looking little boy with long hair and Icy Blue Eyes who creeped the shit out of Ursula and Amaranta when he and his mother came to meet up with them: he showed no shyness around them, walked around the house as if he had been born there, and then asked them for an old toy that he had never ever seen and somehow he knew that they had it.
The childhood antics of the once-Single-Minded Twins Jose Arcadio Segundo and Aureliano Segundo make them border on Creepy Twins. i.e, as their mother was preparing some lemonade, one of the boys took some sips — and the other boy (who had not) told her that it didn't have enough sugar. They may or may have not performed a permanentTwin Switch as kids.
In another of Gabriel García Márquez's books, Del amor y otros demonios (Of love and other demons), one of the two leads is a 12-year-old Lonely Rich Kid named Sierva María. She has such No Social Skills (coming from being ignored by her selfish parents and raised by the family slaves) and exhibits such weird behavior for the standards of that time, that she's believed to either be ill with rabies (after a rabid dog bites her), under Demonic Possession, or under a weird mixt of both.
Although Fiona McDonald in The Highland Twins at the Chalet School is a nice enough girl and not physically frail enough to be a true Waif Prophet, she has visions which unnerve her family - for instance, when she 'sees' her father die, and later, when she 'sees' her brother's plane crashing and he is later confirmed dead. However, she also uses her ability to prove to Joey that Jack, who has been reported drowned, is actually alive.
Interview with the Vampire's Claudia. A vampire who lures her victims to her by ways of sympathy. She's a 50-70 year old woman in the body of a five-year-old girl (and plays up the innocent girl look a lot.) She then 'kills' Lestat by stabbing him repeatedly after she poisons him. Then proceeds to nearly burn their house down.
Roger from Lord of the Flies starts out as a very creepy loner kid. At first, his antics are merely pranks such as taunting, throwing rocks at the smallest kids and kicking down their sand castles. Near the middle, he has become more sadistic and violent and soon becomes the torturer of the group. By the end, he becomes a complete psychopath when he kills Piggy by dropping a boulder on his head. Later, we find out he intends to kill Ralph and mount his head on a pike like he and Jack had done to a pig earlier.
Subverted in the Doctor WhoEighth Doctor Adventures novel The Blue Angel: its alternate reality, theoretically human version of the Doctor "could talk from birth." You know you're scared of the talking newborn, but there's no indication he did anything else that was creepy, and his mother just saw him as unusual and precocious. And played to the hilt in Timeless, in which a little blond girl, possibly older than she looks, and who has crooked eyes and a little dolly, appears where she shouldn't, plays around with the multiverse, gets people killed, knows things she shouldn't, and just acts creepy.
Before The Exorcist, but (mostly) after Rosemary's Baby, some of the best of these stories were anthologized into books: Little Monsters, More Little Monsters, Demonkind and Young Demons. An even earlier collection is called Outsiders, Children of Wonder.
The primary Vord Queen in the Codex Alera series looks like an adult, but she has a number of disturbingly childlike tendencies, such as collecting a group of Alerans into a "dollhouse" where she watches them live and work - and when Tavi rescues them, the Queen goes absolutely berserk. Later on there are a few other scenes that cement the childlike nature of the Queen, including asking innocent questions about simple things she doesn't understand, i.e. expressions of love and affection, and one poignant scene where she cpnfesses to Isana that she only wants her Vord children to survive, like any mother should. This is also a creature that is incredibly fast and powerful and durable, and is trying to wipe humanity off the face of the planet.
Baby Veil in Outcast of Redwall was pretty unnerving. When anyone tried to pick him up, he bit them and happily licked up their blood. He grew up into a common-or-garden delinquent, which was actually something of a relief. Until the poisoning incident, anyway.
Arya Stark in A Song of Ice and Fire starts out as a standard-issue 9-year-old Tomboy. By the time she's 10, she's committing premeditated murder and reciting a nightly list of the people she plans on killing.
She also copes with being deliberately blinded albeit temporarily with disturbing calmness—and refuses to ask to have her eyesight restored because that would be the end of her training to be an assassin.
Jodi Picoult's novel Salem Falls has Gillain Duncan. Although technically a teenager at the time of the novel, she still fits this trope to a T, and it's stated from a former therapist of hers that she was just as disturbed when she actually was a child. Picoult herself has described Gillain as one of the creepiest teenage girls she's ever come across in fiction.
In The Pale King, Mr. Manshardt's infant has a terrifying expression on its face and the body language of an adult. It can also talk, though the person who heard it may be insane.
The Baby from Remnants. It looks like a somewhat creepy two-year-old child, but seems to have some bizarre intelligence and psychic control over its mother, who gave birth to it while in suspending animation for 500 years. It turns out in reality, the Baby is a Shipwright in disguise.
Then there is Harelip, the twin's neighbor who is only sightly older then them and well.. let's just say she has a lot more sexual issues then a young girl should.
Willie Connolly in J.R. Lowell's Daughter of Darkness. She's such a perfect, perfect little girl... and such a nice high IQ too! Her dad must be awful proud... gee, isn't it too bad her mommy killed herself? Aw, isn't that cute, she collects dolls...
Richard and Melanie Cutler in the Cutler Series. They not only bathe together (at age twelve) and share the same toothbrush, but Richard does everything he can to get nine-year-old Jefferson in trouble, destroys Christie's piano, they both play up their being sick in one scene to get their cousins and nanny in as much trouble as possible, and after Christie and Jefferson are returned to the house after running away, Christie sees the twins have ripped her clothes to ribbons, mixed all her cosmetics and perfumes together, destroyed her belongings, Richard laughs at her through the keyhole and tells her to jump out the window...and in their last scene, Richard calmly tells Christie that their mother said the hospitalized Jefferson will die. His sister just stares at Christie, "like some coldly analytical scientist" to see what her reaction will be. It's kinda satisfying when Christie responds by throwing their hot soup in their laps...
Tash Arranda of Galaxy of Fear shows flashes of this from time to time. She's an untrained Force-Sensitive and tends to finish too many sentences that other people start, make too many accurate predictions, and just in general knows things she shouldn't for a lot of people who spend much time around her to feel comfortable. Since she's one of the viewpoint characters, we see that most of the time she's not even aware if she's being creepy.
The Kingdom and the Crown has the eldest grandchild of David ben Joseph, Esther, who is referred to by her family as their enigmatic little sphinx.
In Andre Norton's Dread Companion, Bartare. Kilda's original impression is confirmed when Bartare knows her father is dead before she is told, and it develops from there.
Coira in White as Snow, who scares her nursemaid by refusing to talk for long stretches at a time.
Ivy Carson, in Zilpha Keatley Snyder's The Changeling, is not really creepy, but Martha's family feels "there's a strangeness about her" that they dislike. The author leaves it ambiguous whether this is due to Ivy's appearance, her intimate knowledge of esoterism or that she really is a Changeling.
In the Paradox Trilogy, Captain Caldswell's daughter Ren. She won't speak to anyone but Caldswell, spends most of her time playing chess by herself, and shows signs of psychic powers. Brenton's "daughter", Enna, is exactly the same. All the girls called "daughters" are daughters of Maat, enslaved for their immense psychic power and mentally unstable as a result.
The wraith from Shaman Blues used to be this in life. She was a seven-year-old girl who, apart from this whole "murderess of seven people" thing, would mentally torment adults and children alike and had sick fascination with death and death magic. One of the witnesses recounts years later that his sister once told him that this girl was "an adult, but looking like a child".
Alicja in The Girl from the Miracles District. She has strange visions and portents, often speaks in riddles and doesn't play with other children. It does not help that her unnaturally serene way of being sends chills down people's spines.
Esme of The Witchlands is a young teen who's both able and eager to brainwash witches into becoming wild, murderous puppets under her control.
"The Veldt": Peter and Wendy Hadley, who've replaced their parents in their minds with the AI controlling the house they live in and who fantasize about lions killing their real parents. Even the child psychologist who sees them is creeped out.