Hm... I don't know if I saw this topic a little late but I usually love villains from series, so I had to leave a reply here! I don't read nothing at all that's not seinen/shonen, but I have some in these genres to recommend:
Berserk = Actually a lot of people love the villain in this manga... Although it takes some chapters to his appearance.
Bleach = I just loved the main villain in this series, but I'd not recommend it if you're not patient with shonen. Villains from this manga are very popular among fans!