Sibling rivalry is a common experience for both real people and anime characters. Most fights revolve around small things like who gets the last cookie or who has to do the dishes. While bigger issues can occur, they usually don't involve one sibling trying to destroy the world. But that's exactly what anime heroes with evil siblings have to deal with. Their sibling isn't just annoying - they're potentially lethal, and they have to be stopped.
Some of the villainous siblings on this list are actually evil. In JoJo's Bizarre Adventure, Jonathan Joestar's adoptive brother Dio is a flamboyantly and fabulously cruel person who ends up terrorizing the entire family for generations. In other cases, they're not really evil but have been forced into committing cruel acts. It's not exactly Sho Kusakabe's fault he was kidnapped and brainwashed by a cult in Fire Force, and it'll take him some time to get over it. Either way, these pairs of siblings find themselves on the opposite sides of major conflicts that put their relationship - and their strength - to the test.