Source: batman.wikia.com

6. Mr. Zsasz

(Batman, DC Comics)

At a certain point, Batman writers just started taking the challenge of creating new villains as an exercise in topping themselves. “Oh, you thought Amygdala was a big, strong guy; wait until you get a load of Bane!” “Oh, yeah, if you think Ra's Al Ghul was the smartest villain we could come up with, come check out Bane!” “Yeah, well, you know who's a better strategist than Cluemaster?” You get the point; most of them were just Bane.

But the one that wasn't was Mr. Zsasz.

Zsasz was a riff on the good ol' themed killer. He makes tally marks on his body for every murder. That's almost cartoonishly grim and dark. Like, if you had to mock how self-serious Batman comics got for a while, all you'd have to do is put Zsasz in front of a screen and portrait light him.

Say what you will, they haven't figured out a way to make a crazier villain since Zsasz. Except Ban…Wait, never mind.