Definitely Necromancy.
For starters, I'm lazy, so conjuring up skeletons and zombies to do the work for me is perfect.
2nd, think about all those other powers, since skeletons and zombies are mindless, don't breathe, and don't feel pain, psionic abilities and a whole bunch of those other disciplines wouldn't even affect them.
3rd, once you kill your opponent, you get to really rub it in by resurrecting them and making them do your bidding!
That and the Necromancer was my favorite Diablo 2 character class, and Quan Chi is my favorite MK character (obviously).