I was actually thinking, in descending order, Joker, Batman, Two-Face, Riddler, Scarecrow.
Joker: Why so serious? I thought it was a bit obvious right there. Guy based around using fear effects, makes bombs, and uses knives for massive damage when his enemies are disabled. Avenging executioner would have greatly enhanced this build, but alas.
Two face, besides using the quote, was supposed to be a guy who could do anything at any time, basically doing a different random thing each day very well.
Batman used his sneakery, mobility, martial prowess, and shuriken to destroy his enemies. Why does the joker want to kill him?
I admit riddler was quite cryptic, but I chose the three classes likely to be good at riddles (bard, archivist, and wizard). He's mostly bard, and he uses his other two classes to create his baffling criminal pranks.
Scarecrow was also really hard, but he's got a definite fear focus with the hexblade and necromancer, and he did build his mask.