Here are some of the villains from Amadeus' gallery. Others may arise, but the ones I could think of at the moment were these.

Joker

Lex Luthor

Clayface

Firefly

Bane

Solomon Grundy

Scarecrow

Ra's Al Ghul

Grodd

Brainiac

Doomsday

Chronos

Darkseid

Mongul

Hro Talak

Vandal Savage

Felix Fausto

Project Cadmus

Toyman

Metallo

Among Others