Shadow. More specifically Finger of Death (read the tooltip if you don't remember it)
Grammer nazi's aren't a per-requisite for you're enjoyment of these signature. Although for all intensive purposes its really a mute point, per say.
Lightning + Armour = ???
Can't post links so just search youtube for Arc Attack
(the answer is 'awesome')
I'd go with priests shadow magic... shredding the mind, and can most likely make the body feel the pain of all the other magics ever, at the same time.
Holy by far. Paladins can do terrible things to a sinner. There's a reason the undead are terrified of it.
I'd put Shadow a close second, then all the physical magic after that with Frost last.
I dunno, I think Nature magic could be a contender for top slot, I mean nature can be pretty brutal in the real world, I wouldn't want to mess with it.
David Blaine and Criss Angel are pretty painful to watch.