We know about the Evil Uncle. It looks like nephews in these families have a difficult time.
But don't think that uncles always have it fine. Sometimes they can be the ones who have trouble. This trope is for uncles who get badly treated, sometimes they are the Butt-Monkey, sometimes they are subject to avunculicide, the act of killing an uncle.
This can happen when the nephew is the one who succeeds to power and the uncle is still a member of court. But his nephew may be The Caligula and treat the uncle badly.
Often associated with The Evil Prince.
- Fairy Tail has Larcade, the son of Emperor Spriggan, who gave all the love and affection he could possibly give to his own brother, leaving none for Larcade (whose mother was nonexistent in his life). Naturally, when Spriggan deems his brother of no further use, Larcade leaps at the opportunity to slay his hated uncle and finally get in his father's good graces. Subverted in that Larcade isn't truly Spriggan's (aka Zeref's) son, but rather an Etherious just like his "uncle" Natsu, so in a sense they're more like brothers. Larcade has the Dragneel name simply because he was the closest Zeref got to bringing Natsu back to life before he succeeded (ala a prototype).
- In Action Comics #293 Prince Endor of a planet of Sorcerers is nearly overthrown by his nephew Lord Nomed, who uses magic to remove a winged horse's flight, as Endor being unable to lead the procession on a flying horse means he'll lose the throne. Fortunately, Comet the Super-Horse is able to take their place.
- Darkseid came to power by basically arranging a situation where his uncle Steppenwolf, next in line to the throne, was killed in battle with Highfather. Interesting in that everyone in Apokolips is evil. Even the Lowlies, to a degree. Darkseid is just the most evil figure out of all of them.
- Subversion: The British ITV book "Look-In" featured Danger Mouse stories featuring Hopalong Casually, the "white sheep" nephew of Baron Greenback.
- In the Doctor Who Fanfic "Weapons of the Daleks" Colonel Vimot Lupib kills his Uncle General Jyot Lupib to prevent the war ending. He then blames the Doctor for it, and attempts to seize his uncles' position on the Military Council.
- Prince Jewelius, the main antagonist of the My Little Pony: Friendship Is Magic fic Loved And Lost, usurps his aunts Celestia and Luna by defaming them along with his cousin Cadance and some of the other heroes, driving them away from Equestria. He later confesses to have secretly hated the more popular Celestia and Cadance for years. He very nearly manages to have Celestia publicly hanged, and during the climax, after rejecting her reconciliation offer, he comes close to decapitating her himself.
Celestia: I don't understand. The nephew I raised would never be so cruel to anypony, especially his own family!
Jewelius: The nephew you thought you raised never existed! Love, family, friendship! You think I really cared about all of that?! I only choked down all those 'happy' moments while standing in yours and Cadance's shadows! But no more. Now I will be the only one who will cast the biggest shadow!
- In the Godzilla franchise, Space-Godzilla would qualify, being as he is the son of Biollante, who is, technically speaking, Godzilla's sister.
- In Star Wars Episode VII The Force Awakens, Kylo Ren aka Ben Solo is this to his uncle Luke, having destroyed the nascent New Jedi Order and emotionally destroyed Luke so much that the man swore off everything and went into hiding.
- The antagonist of The Lost World: Jurassic Park is John Hammond's nephew Peter Ludlow, who's trying to create a new park against his uncle's wishes and is much more of a Corrupt Corporate Executive than Hammond (who is by no means innocent himself but is generally portrayed as more of a misguided Uncle Pennybags in the films.)
- The Great Warrior Skanderbeg: Hamza Kastrioti to the title character. Tragically, he doesn't even start out evil since his uncle is pretty much the closest thing to an father figure he has, but Hamza becomes jealous of Skanderbeg's feats and gets corrupted by the bad guys into betraying him when they say he will be sidelined and passed over as his heir when his uncle begets a son. The movie's final battle ends up being fought between uncle and nephew.
- Follow Me, Boys!: When Hetty decides to donate valuable real estate to the local Boy Scout troop, her nephew Ralph tries to have her declared mentally unfit so he can take the land and develop it.
- In Dragon Bones, everyone thinks Ward is this and intends to kill his uncle in order to inherit castle Hurog. He isn't, and is quite a bit frustrated with everyone so readily believing that he would do something so horrible.
- In Herodotus' Histories, Xerxes (yes the one from 300) has elements of this. When his Uncle Artabanus criticises his plan to invade Greece Xerxes tells him to stay at home with the women and says that if Artabanus wasn't his uncle he would suffer even more. Then averted, as the next day Xerxes has reconsidered and apologizes.
- King Arthur from the legend was betrayed and ran through by Mordred, who in some legends is his nephew through a sister.
- Geoffrey's History also has Cordelia (who inspired the character in King Lear) getting overthrown by her two nephews Cunedagius and Marganus and killing herself in prison. However those two turn out to be terrible cousins, and after the older one, Marganus, tries to take the other half of Britain Cunedagius kills him.
- Arthur's cousin and successor Constantine III of Britain is also overthrown by his nephew Aurelius Conanus, who imprisons another Uncle that should have succeeded and kills both their sons.
- King, Queen, Knave by Vladimir Nabokov has Franz intend to murder his uncle; the narrator tells us that later on he will be "guilty of worse sins than avunculicide".
- Happens in How to Train Your Dragon with Stoick, as his nephew Snoutlout has been made Chief while he has become a slave.
- Joffrey Baratheon in A Song of Ice and Fire, especially to his uncle Tyrion. He insults and humiliates him at every opportunity, threatens to rape their wife (his aunt by marriage), and serve her her murdered brother's head, and even possibly plotted to have him killed. Ironically enough more people in Westeros think Tyrion is the evil one, blaming him for his nephew's bad reign and Joffrey's death. Tyrion ends up saying though he didn't kill his nephew he wishes he had and took a lot of pleasure in watching them die.
- Jaime wonders if his sister Cersei will be an Evil Niece and be prepared to have their uncle Ser Kevan Lannister murdered as he seems to know about their affair, and later he helps remove Cersei from power. Later, when Varys murders Kevan he says the Tyrells will blame Cersei for it.
- From "The Dance of the Dragons" there was no love between Prince Aemond and Prince Daemon, whom he considered something like his Archenemy, and spent precious time trying to defeat his forces. Their eventual duel was the climax of the Dance of the Dragons. Granted, Daemon was himself a massive jerk and Evil Uncle, but he didn't have the same psychotic cruelty of Aemond.
- In "Wyrd Sisters", the ghost of King Champot of Lancre mentions when he was asleep his nephew chopped his head off.
- Voldemort, the Big Bad of the Harry Potter series. He framed his Uncle Morfin Gaunt for the murder of the Riddle Family and altered Morfin's memories so he believed he'd done this, meaning Morfin spent the rest of his life in Azkaban. Of course, Morfin himself was a violent Pure-blood fanatic, but Dumbledore notes he still didn't deserve to die in prison for someone else's crime.
- From The Silmarillion by Tolkien is Maeglin. He is the sister-son of Turgon, King of Gondolin. As his love for Turgon's daughter isn't permitted he rebels against his Uncle after Idril marries Tuor and ends up betraying Gondolin to Morgoth, leading to Turgon's death.
- Fear, Loathing and Gumbo on the Campaign Trail '72: Mao Yuanxin, Mao Zedong's sadistic nephew. He ends up drugging and isolating The Great Helmsman, turning him into his puppet so he can take control of China.
- Game of Thrones: Joffrey plotted the assassination attempt on Tyrion at the Battle of Blackwater; Ser Mandon Moore carried out his order. Joffrey continually goes out of his way to humiliate and bully his uncle... ironically, Tyrion is looked upon as the evil one.
- Caligula from I, Claudius. He treats his Uncle Claudius badly, among other acts. He humiliates him, forces him to be the doorman at a brothel, and has him thrown in a river. Caligula also plots the murder of his Great-Uncle Tiberius, though not actually performing it.
- Apparently the last ruler of the Shang Dynasty, Zhou Xin, was like this. When his Uncle Prince Bi Ghan criticised him he had Bi Ghan's heart cut out as sages were supposed to have seven openings to the heart and he wanted to check this. His other Uncle Ji Zi feigned madness and was imprisoned.
- In the Near Eastern Story of Ahikar, the earliest version of which dates to 500 B.C.E., the title character, a chancellor to the Assyrian king Esarhaddon, adopts his nephew Nadab and raises him to be his successor. However, the ungrateful Nadab falsely accuses his uncle of treason, and Esarhaddon sentences Ahikar to death. Ahikar talks the executioner into presenting the king with another executed prisoner's body while he goes free. The earliest text breaks off at this point, but later versions of the legend have Ahikar emerge from hiding, clear his reputation, and deliver a "The Reason You Suck" Speech to Nadab, who promptly dies.
- Odin and Loki in original Norse Mythology were blood brothers, despite what is shown in Marvel Comics. One of Loki's sons, the Wolf Fenrir, would eventually devour Odin at Ragnarökkr. And for the Comic version another of Loki's sons, the Midgard Serpent Jörmungandr would eventually kill Thor, though die itself.
- Then with King Arthur, there is his evil nephew and son Mordred, illegitimate son of Arthur's half-sister Morgause or half-sister Morgana. Mordred would kill Arthur in battle as Arthur killed him.
- Gender Inverted example; when Jade Chan from Jackie Chan Adventures (temporarily) became the "Queen of the Shadowkhan", she acted like an Evil Niece to her Uncle Jackie.
- Inverted with Poindexter, the good nephew of the evil Professor in the 1950's Felix the Cat cartoons.
- Paris Franz, the villain in the prologue of "The Killing Joke". He tries to steal money from the bank account of his uncle, a mob boss, then when they retaliate against him he has them assassinated, leaving their body for Batgirl to find.
- Subversion: The made-for-TV Felix the Cat cartoons featured Poindexter, the nephew of the evil Professor. Poindexter assists Felix on many adventures, much to his uncle's dismay.