How should I model this character?

I see him in a long black leather or vinyl coat. I also see him as someone almost angelically beautiful, with longish silky hair, large black eyes and delicate features, to sort of contrast with the evil inside. People who would just see him in the street would be drawn to him because of his looks and charisma, but you could say that he is almost childlike: capricious and violent like a little boy who breaks his toys for the fun of it. Only the toys are all inhabitents of the planet. I would like to see him opening himself to a character you would have created, someone like an 'onee-chan' (older sister) who's been in his life for a long time and who he's spared out of some kind of twisted attachment. Somebody fairly strong who is also able to fight, but who can also bring out rare moments of tenderness in the evil character, and who cares for him in her own way. This would give more depth to your character. You could also give him a past: where he grew up, what kind of family he was in. You could choose to make his evil tendencies relate to negative experiences he's lived when he was small, or to just keep him pure evil, but I suggest you give him a redemption at the end of the book because no one likes one-dimensional characters. Good luck!!