I've been thinking hard about this question for Nakama Intro Week since the anime mod staff first suggested it: who would be your anime rival / enemy? Here we go!
Basically any of the anti-heroes from Fairy Tail XD
I'm counting Gajeel & Juvia in this, too. Why? Because 1) I like that villains really die at our heroes hands directly in Fairy Tail. I don't like killing xD and 2) I like that many villains aren't so evil, just misunderstood or misdirected, and they come around. I am fine with having dozens and dozens of villains as long as I can make their world a bit better by defeating them XD