My favorite villains so far:
1: Talon. He's so cool and complex, and every scene with him and Damian is very well crafted. He's got a cool look and he fights in such a badass way. He resonated with me exceptionally.
2: Hank Henshaw. He's understandable, really petty, and has a cool look. He really resonated with me, it's hard to explain.
3: Deathstroke. He's so badass and his two main appearances really cement him as a really bad guy and such a cool villain. He also has solid motives.
4: Darkseid. He's just really imposing and cool. I love his voice when Steve Blum voices him.
5: Brother Blood. He's voiced perfectly and he's just really cool and smart.