Who's your favorite comic book villain and Why?
I have MANY favorites but I'll pare it down to one: Doctor Doom.
I like him because he's an evil genius and overlord who's regal, larger than life and has an ego the size of the national debt. One of the original masterminds in comics, he's one of the few villains who has a very real chance of pulling off his ultimate goal: conquering the world (and has done so on occasion).
Equipped with a genius level intellect (his mind is his MOST dangerous weapon and he's one of the smartest people in the Marvel universe), a will of iron, a mastery of science & technology matched by few and no small skill concerning sorcery and the occult (people tend to forget that) - he can defeat ANY opponent he comes against, especially if he knows they're coming...
Oh don’t get me wrong now; I’m a big DC fan too (I love the Vertigo line in particular – Fables rules the earth), along with Dark Horse (mostly Hellboy and Conan) and Image (mostly The Walking Dead). It just so happens that one of my all time favorite villains resides in the Marvel universe.
Some of my favorite DC villains:
Mister Freeze (the modern version, not the dopey, 1960s version)
Killer Croc (cuz I love monsters)
Clayface (Matt Hagen – that monsters thing again)
Lex Luthor (gotta like those evil genius masterminds)
Live Wire (I like electricity based powers and she was hot when voiced by Lori Petty)
Harley Quinn (she is just super-hot)