I think the Joker should be off limits, X.
I don't think I have a proper correlate for myself here. I'd like to be Jerome Valeska, but I don't know.
As for others...
I think Tryp would make a better Hugo Strange, maybe.
Ones I wonder who would fit...
Victor Fries/Mr. Freeze
Scarecrow = Turncoat
Harvey Bullock
Oswald Cobblepot/Penguin
(Will enter them when I think of the right person.)
Time to throw some of the more unusual ones into the mix:
Clock King
Clayface
Mad Hatter
Firefly
Calendar Man
Ventriloquist
Ra's Al Ghul
Zsasz
The Creeper
Cake stated: source post
Dexter is Joker.
When did the Joker become an autistic retard...