Trigun

The anime and manga called Trigun doesn't have much in common with Oni, except for the fact that they both take place in the future in a world that is inhospitable to human life, there are two siblings with powers that separate them from ordinary humans, the main character has a transformation he/she can't fully control, and the main villain is his/her brother who hates humanity and shares the same hair color….

Knives and Muro

The nemesis of the main character, Vash, is his brother named Knives Millions. They are both independent "Plants", a normally-passive bio-engineered life form used as a sort of power supply by humans in the future. As a child, Knives first sees the ugliness in humans and learns to hate them. As an adult, Knives is on a mission to eradicate humans from the planet on which they have all settled. Vash, on the other hand, continues to care for humans despite their flaws. This disagreement eventually turns them into bitter enemies and forms the basis for the plot.

Knives and Muro seem to have hatred of humanity in common, considering that at the end of Chapter 14 Muro tells Konoko, "Join me or die like all the others, choking on dead air and foul water." Even though Konoko initially thinks his plan is to gain power over humanity by offering the Chrysalis as their only escape from the encroaching pollution, Muro doesn't seem to care if they ever get one. Does he actively want to exterminate most of humankind or is he just totally apathetic? Perhaps he recognizes that if anyone can get a Chrysalis and advance to the Imago form, he'll lose his physical superiority over humanity.