Toss up between Two Face, Scarecrow and the Riddler, but I went with Enigma.
Joker
Two-Face
Riddler
Scarecrow
Poison Ivy
Mr. Freeze
Bane
Ra's Al Ghul
Mad Hatter
Catwoman
Harley Quinn
Penguin
Black Mask
The Ventriluest
Other.
Toss up between Two Face, Scarecrow and the Riddler, but I went with Enigma.