"When it comes to Gensokyan sisters, in general the younger one is "broken"."
In most games, if the Big Bad has a sibling, he or she will be even stronger than the Big Bad themselves. Mostly these appear as Bonus Bosses, but in some cases they may serve as a plot twist. This is a natural consequence of the Sorting Algorithm of Evil; if you find yourself fighting a bad guy's relative later on, that relative will necessarily be tougher in order to keep pace with your increased skills.
Not to be confused with the Cain half of Cain and Abel. Also, many of these are big spoilers, so read with caution.
See also Always Someone Better, Aloof Big Brother. You might find them Avenging the Villain.
—ZUN, Touhou
Some examples are:
Anime and Manga- An Anti-Hero example, Nanami from Katanagatari is by leagues stronger than her brother Shichika. When she was younger, her father refused to train her in the Kyoutoryuu style, not because she was a girl, not because she was always sick, but because she's far too strong for him.
- A Dragon Ball Z Non-Serial Movie is based on Freeza's stronger older brother Cooler showing up on Earth to kill Goku for killing his brother. (Goku hadn't actually killed Freeza, but Cooler didn't know that.) Ironically, Frieza gets revived much later on and becomes the stronger sibling again, though Cooler still beats him in savviness and having a Super Mode that doesn't bleed stamina like a punctured water balloon.
- The Gorgon Sisters from Soul Eater and Soul Eater Not!. Medusa, Arachne, and Shaula are savvy, manipulative, experimenting, animal themed, hot witches who each held the title of the lead antagonist at different periods and otherwise act to one-up each other, the good guys and even more villainous factions.
- Inverted in Mobile Suit Gundam SEED and Mobile Suit Gundam SEED Destiny, where Destinys Rey Za Burrel is the younger, less insane "sibling" of SEEDs Rau Le Creuset. Where Le Creuset was the Big Bad and sought the destruction of the human race, Rey's a Well-Intentioned Extremist who believes Utopia Justifies the Means, acts as The Dragon to new Big Bad Gilbert Durandal, and isn't nearly the physical threat that Le Creuset was.
- In Fullmetal Alchemist, the younger brother Alphonse has been always stronger than his brother Edward in combat, even before he became a suit of Animated Armor. On the other hand, Edward is the better alchemist and uses it in battle, too.
- For the majority of InuYasha, the titular character is weaker than his half-brother and full-blooded demon Sesshomaru.
- Played with in Getting Back on Your Hooves. Trixie's elder sister Checker Monarch is far more dangerous than she is due to being a Sociopath and exceptionally skilled with the power she has, but Trixie has more sheer power than her.
- In the Pony POV Series:
- Discord is revealed to be the youngest of the Draconequi, and his elder sister Strife is a much better fighter than he is and his older brother Destruction has used a nuke as an opening attack. At present, however, Discord is the strongest of the siblings because he ate Destruction and an Avatar of his father Havoc.
- It's revealed that Chrysalis is technically siblings with Makarov (Pandora created both of them), and Makarov was a Reality Warper.
- In the seventh The Fast and the Furious movie, the villain is the "big, bad brother" of the one from the previous movie.
- Joe Bob Fenestre from Animorphs reveals he has a 'prime' sibling in The Warning. It's none other than Visser Three, main villain of the series.
- Lampshaded in Harry Potter and the Chamber of Secrets when, after Dobby tells Harry that Voldemort is not responsible for the shit hitting the fan this year, Harry asks whether Voldemort's got a brother.
- Older Than Steam: The Arabian Nights version of Aladdin has the Big Bad's brother (also an Evil Sorcerer, the vizier is more an Obstructive Bureaucrat in this one) as the villain of the second part, and far more powerful.
- The Elder Princess Shroob in Mario & Luigi: Partners in Time.
- Flandre Scarlet from Touhou's sixth game, Embodiment of Scarlet Devil (her sister, Remilia, is the game's last boss).
- From a much earlier game, Lotus Land Story, Mugetsu is the extra stage's first boss and Gengetsu is the extra stage's second boss. Though having no last name, official material states that they are twins.
- Shizuha Aki is the midboss to Minoriko Aki's stage in Mountain of Faith. They're both still ridiculously weak, though, being the bosses of Stage 1.
- And in Subterranean Animism, Koishi Komeiji (Extra stage) to Satori Komeiji (fourth stage).
- In all of these cases, it's the younger sister who's stronger. Significantly so in the cases of Flandre and Koishi.
- The only exception of the stronger younger sister is Gengetsu, Mugetsu's older twin sister in Lotus Land Story, who is infamous for her nigh-impossible to dodge time-out phase bullets. Word of God claimed that she's the strongest boss by virtue of this phase alone.
- Death and Schirach from Romancing SaGa. Death is the most powerful physically and controls Necromantic magic, and Schirach has the most powerful magic of the Trio of Dark Gods. However, if you power up the Big Bad to its fullest then the point is rendered moot.
- Hooktail in Paper Mario: The Thousand-Year Door actually has two other siblings. Gloomtail, who is her brother and is basically a Palette Swap. Bonetail is the eldest of the group and is an undead dragon lurking in the Bonus Dungeon.
- Final Fantasy XI: After defeating Archduke Kam'lanaut halfway through the Rise of the Zilart missions, you find out that his comparatively pint-sized brother Eald'narche is really his big brother and serves as the Final Boss at the end of the mission set.
- Of Resident Evil – Code: Veronica's Ashford twins, Alexia is the smarter and tougher one as well as the Big Bad in their game of appearance. Before she wakes up from a deep freeze, you're led to believe she's actually dead after finding out that whenever you see her beforehand it was her brother, at first the primary antagonist, impersonating her, so her arrival does serve as a turn.
- Resident Evil 5 also does this with strong implications that there's another Wesker that's more clever and less hammy than the one we all know. Check the files in chapter 6-2 and Lost in Nightmares, it's sad indeed.
- In MOTHER 3, Claus is the Mysterious Masked Man, and proves to be much stronger than your entire party.
- Played for laughs in Earthbound. In Deep Darkness, there's an enemy called the Manly Fish. There's a stronger, rarer enemy called the Manly Fish's Brother.
- Rick and Nick Bruiser in Super Punch-Out.
- A variation with a different relative. In Loco Roco 2, the final boss of the main game isn't the Big Bad of the first game, Bon Mucho—it's his mother, Majoline.
- In Rosenkreuz Stilette, Zorne Sepperin is the adoptive older sister of the Big Bad, Iris Sepperin, who has inherited Rosenkreuz's godly powers.
- Undertale: Sans is much stronger and smarter than Papyrus, on the rare occasion when Sans decides to stop bumming around the house and actually do anything. One such occasion being, if the player decides to go for a Kill 'em All ending...