I'm unsure if you mean "kinks they have" or "kinks they're meant to appeal to" so I'll answer the former! If you mean the latter, please ask again, because that's a whole different can of worms that requires a longer response.

Alec's core kinks are sadism (both physical and psychological), corruption/manipulation, and dubcon/noncon. He's also extremely into blood, gore, and death. Viola is dom4dom with Alec, the defining sexual relationship of her life, and likes co-dominating with him. She's also a raging hybristophile (fetish for crimes committed by her partner) and a sadomasochist. Isabelle is an extreme submissive, masochist with a dash of sadist, and a rope bunny. She's also got a major thing for guns and weaponry.