*throws Squirrel Girl at Deadpool*
Just because of this:
http://sketchcardsaloon.com/2011/02/27/yes-it-is-true-squirrel-girl-beat-deadpool/
After seeing that image, you'll never again think of fingernail scratching as a weak attack!
I didn't see the part about villians, so here's my answer for that one:
Doctor Doom.
I like the idea of a villian who's not the typical "evil psycho" type.
Doom is cultured, polite and above all practical.
I bet he has a copy of the Evil Overlord's list to hand and reads it well!
Plus, he's a genius, so it's not all about power and strength with him, plus his devious mind.