Catwoman, Batman, Batgirl, Nightwing, Bane, Joker, Harley.
I'm a villian player, but I am less likely to complain about the low tier being overpopulated with villains (just because they're bad guys shouldn't make them bad characters!), and more likely to worry about the imbalance of Batman based characters....
And is anyone else confused why Scorpion is considered a hero?
I just can't imagine him saving puppies from burning buildings, at least as much as I can imagine him putting a large amount of puppies into a building, then burning said building...