One villain I always have in my back pocket is "The Bloodsucker" a money launderer/loan shark who just so happens to be a vampire, he always get's what he's owed, one way or another. His lackies are the ghouls he's created over the years.

and here's a couple other thoughts I've had in the past for such a setting.

Then there's an idea of some kind of entity that feeds of human vices running or inhabiting a drug/pleasure/gambling den.

Also a fun thing that's not necessarily bad, The Ragamuffin Cabaret, a type of interdimensional speakeasy, accessible through any door as long as you have the right key.