Sometimes you get lucky, and the Mysterious Waif you adopted becomes a well-adjusted and welcome addition to the family. Other times...not.
For the sake of the story, the young couple will have no idea anything is wrong, but tropers will know right away there's something not right with this newcomer. She's a Creepy Child, who looks like she strolled out of the Uncanny Valley. It's not long before things start going wrong around her. Pets start acting up. Things go missing. There are fires. Injuries. Nocturnal birds of prey show up everywhere.
As if they don't have enough to worry about, the couple's biological child is making up crazy stories about how the orphan is planning to kill them all in their sleep! They will be ignored. Sometimes one or both of the parents figure it out at the very last minute. Sometimes it falls to the children to stop her.
Feminine pronouns are used because Evil Orphans are - like creepy children generally - frequently little girls but evil little boys are sometimes used.
The Evil Orphan is the modern-day incarnation of the Changeling Tale. It uses the tried-and-true horror of Subverted Innocence and the Devil in Plain Sight, as there is little that can compare to the fear and revulsion of discovering that one has been succoring evil incarnate in one's own home.
Expect anything of the Ungrateful Bastard, but be particularly on the lookout for those that play on her youth, like the Wounded Gazelle Gambit. May cause Fridge Horror when the audience wonders just how she became an orphan in the first place. Incorporates any and every trope having to do with with Creepy Children. See also Enfant Terrible.
The polar opposite of the Heartwarming Orphan.
- Dio Brando of JoJo's Bizarre Adventure gets adopted into the loving Joestar family upon the death of his abusive father. Far from being grateful, though, he proceeds to make his adoptive brother Jonathan's life hell, all while looking perfectly innocent to his adoptive father George. After Jonathan beats him up after Dio pushes him too far, though, Dio calms down and becomes perfectly pleasant for seven years... but it's all an act, as he hatches a plot to poison his adoptive father.
- Johan Liebert from Monster combines this with Where I Was Born and Razed. Repeatedly.
- Rosemary from Ashitano Nadja didn't start as this, but she got in the role very quickly after a major Freak Out caused by seeing that her old friend Nadja was the one living her formerly innocent dream.
- While Orochimaru of Naruto didn't defect from Konoha until around 10 years before the start of the story, the Third Hokage noticed there was something unsettling about him after he lost his parents. He largely turned a blind eye to it because of his talent.
- Mukuro from Reborn! (2004) is adopted by another family but soon uses the man taking care of him to kill off the entire family.
- While the audience knows that her orphan status has nothing to do with her sociopathic and sinister nature, other than Being-X, no one else knows anything about the history and origin of Tanya Von Degurechaff from The Saga of Tanya the Evil. As far as anyone in-show is concerned Tayna is just one of an innumerable amount of war orphans in their country. And considering she joined the military at age 9 (and continues base her decision to join on her status as an orphan), there is nothing else for them to go on regarding the source of her sadistically ruthless personality.
- In The Liar, all of the foals at the orphanage where Trixie lived bullied her relentlessly, although it's debatable if they could be called truly "evil". But even if they don't qualify as evil, Snowbank unquestionably does. He pretended to be nice to Trixie to gain her trust and then framed her for beating the crap out of a filly named Peach Blossom (who is no victim, either—she cooperated with his plan, letting him cast a spell to put fake bruises on her body). His plot worked flawlessly, because the matron didn’t even try to look for proof that Trixie was the one who hurt Peach before throwing her out onto the streets. The worst part? Snowbank did all of this just so he could increase his popularity with the other foals, who all hated Trixie and wanted her gone. Despite his young age, his actions easily qualify as a Moral Event Horizon.
- Exploited in The Good Son: the evil one is the kid with both parents, but he manipulates the people around to make it look like his innocent, half-orphaned cousin is the bad seed.
- The Omen (1976). The boy, Damien, is an orphan substituted for the couple's stillborn child, who died shortly after birth.
- The antagonist of Thor and The Avengers, Loki, had this trope forced on him, seeing as he was lied to his entire life about his parentage. He doesn't become evil until he finds out he is adopted.
- The whole point of Orphan. Although, in a subversion, it turns out that "Esther" isn't even a child, but an adult woman with a growth disorder.
- Played for laughs in Problem Child. He isn't really evil, just misunderstood and tends to Pay Evil unto Evil.
- ALiCE (2014): Subverted, Michael was much happier when he lived at Woodrow Children's Asylum; being adopted by Joseph and Mary and the abuse he suffered at their hands was his Start of Darkness.
- Discussed in A Brother's Price. In a case of Deliberate Values Dissonance, adoption is seen as "a hidden evil". When a family commits treason, if it's not believed to be divided then every member down to the youngest is killed to prevent a Cycle of Revenge or You Killed My Father situation. There is treason in the book, and while Ren does not want to kill her five-year-old 'niece' Eldie, her sister ruthlessly reminds her that none of the child's relatives will take them, and if they take the child, Eldie will eventually know why their family was killed and turn on them.
- The Great Brain: Franky Pennyworth starts out as this after he's adopted by the Fitzgerald family. He's downright mean to the point of homicidal to JD and his parents, only showing kindness to their housekeeper. As it turns out, the trauma of losing his parents when their house burned down caused Franky to block out the event and come to the conclusion that the Fitzgeralds replaced his family (since the housekeeper had no analogue to the Pennyworths, she was immune to this). JD forces a breakthrough when, tired of Franky's shenanigans and his parents' indulgence thereof, administers a spanking to Franky, breaking him through his mental block and forcing him to confront the memory of the tragedy.
- Harry Potter:
- Lord Voldemort was raised in a Muggle orphanage, where he spent his free time bullying the other children in a variety of cruel and magical ways. He later became a Self-Made Orphan by tracking down and murdering his muggle father and paternal grandparents (and framing his maternal uncle for the deed).
- In Harry Potter and the Cursed Child, Voldemort's daughter Delphi also qualifies, since she was born shortly before both of her parents (Bellatrix Lestrange was her mother) died.
- The novel Hogfather features Mr. Teatime, who was taken in by the Assassin's Guild after both his parents died suddenly when he was very young. In the words of guildmaster Lord Downey, "In hindsight, perhaps we should have looked into that a bit more."
- Heathcliff in Wuthering Heights. His Freudian Excuse is relatively strong, but at any rate, he ends up a usurping beast of pure spite, and his intentions are just that.
- Little House on the Prairie: Nancy Olesen, given her extreme behavior issues and destructiveness. Although it is possible, even probable that Nancy has some very dark secrets in her past, the main reasons given for her extreme destructive, mean behavior center on her being moved from orphanage to orphanage due to her behavior problems (resulting in an unstable life) and the death of her mother while giving birth to her (a condition that today is known as pre-eclampsia). Indeed, in her first episode, Nancy – who deep down likely knows why her mother is not part of her life – claims she was abandoned by her dear, sweet mother.
- CSI has the very Creepy and Insufferable Genius Hannah, whose parents have died (the details are never explained) by her second appearance. In her first appearance she gets her brother off a murder charge (albeit an accidental one). In her second she frames him and Drives Him To Suicide to keep him dependent on her. She also Breaking Speeches Sara, possibly contributing to her decision to go on a vacation to the rainforest.
- Supernatural has a young girl in the first season who not only cut the throats of her biological and adoptive families, but made it look like her adoptive father did it. Then she did it to people who owned a painting of her adoptive family.
- Considering how ugly that painting was...And that they knew it has a bad reputation of previously deceased owners...Maybe they had it coming.
- Alexander on Smallville is an infant clone of Lex Luthor. Tess Mercer hoped that by raising him to be good, she could save him from the Luthor legacy. Unfortunately, Alexander has all of Lex's memories, and is aging very rapidly to boot. As of "Luthor" he's gone AWOL, and is out there, somewhere, plotting revenge on her and Clark. Eventually inverted, since he ended up losing these memories and becoming Superboy.
- Cindy Caine from Universal's Halloween Horror Nights is this in her third backstory. She was a mentally unstable young girl who was driven off the deep end by abuse from the other children and ended up burning down the orphanage, killing everyone but herself. She was later found and adopted by Dr. Albert Caine, a man just as insane and murderous as herself.
- Orphan, the Final Boss of Final Fantasy XIII, as much as a mechanical demigod can be considered an "orphan" anyway. Representing the fal'Cie's feelings over being abandoned by the god that created them, Orphan and his fellow fal'Cie manipulate the heroes and cause a massive amount of death and destruction in a convoluted plan to reunite with their maker, which they are not treated as sympathetic for at all. The motif is even integrated in Orphan's design—the first phase of his boss fight consists of a baby's face surrounded by a mother and father figure, and the second phase, Orphan's Clipped-Wing Angel true form, consists of just the baby's face, as if he was abandoned by his parents.
- In Mission Critical, you find The Mole's secret diary, where he explains his reasons for betraying The Alliance to the UN. His parents were scientists. He and his brother were visiting them at work one day, and a batch of nanites programmed to clean up oil spills was accidentally let loose, and his parents (or rather, all oils in their bodies) were eaten from inside out right in front of them. From that moment, he decided that the UN was right in limiting technological development.
- Clive in Professor Layton and the Unwound Future, who lost his parents in a time machine explosion 10 years ago, and schemed to take vengeance on the people responsible with the money he inherited from his adoptive mother.
- Whole bunch of them in Rule of Rose, though all have their own Freudian Excuse, and you will end up feeling more pity than loathing for them by the end. Wendy tops all the others by making the others kill Jennifer's dog, and then setting a serial killer loose on the orphanage. All because Jennifer didn't love her alone.
- During a questline in World of Warcraft Alliance players encounter Hope Saldean, a friendly young lady who was adopted by the Saldean couple four years earlier. While Hope seemingly spends much of the Westfall-storyline feeding the homeless, a shadowy figure is gathering the old members of the Defias Brotherhood. In the end Hope reveals herself to be Vanessa Vancleef, the daughter of Defias leader Edwin Vancleef, who has been secretly plotting against the Kingdom of Stormwind the whole time.
- Family Guy spoofs this with Stewie's pet turtle.