Are you kidding? He did it constantly in Nibelheim, right up to the point where he skewered Cloud.

Sephiroth would Supernova his ass out of the Nintendo exclusivity, lol.

No, no he didn't.  He never laughed while doing any of that, he just killed numerous people without emotion.  I seriously don't know where you're getting this from.

http://www.youtube.com/watch?v=dlYQGpZlLPU

Here's some proof. Don't mind the funny character names :) I'd say Sephiroth is pretty composed.

Actually he does laugh.....at the very end.

I think Ganon would win because he fights for himself and cares for no one. While Sephiroth fights for Jenova and really cares about Jenova. Add the fact that one is experiment by humans that caused him to become evil,while the other was born pure evil.

Of course he laughs every now and then in a maniacal tone to taunt Cloud or when he's actually talking to people in a conversation. But the point still stands that he doesn't laugh 'insanely' while killing people.

Gannondorf the King of Evil.

 Yup, Ganon is hardcore. He's a crack dealer and pimp at heart.

He'll also steal your newspaper, egg your house, and kick your dog.

sep or course we know a lot more about seps personality than gadon

I've been through this an variations before and I always say Ganon. The immortal, invincible, with power granted to him by a deity that represents power.

If nothing else he wins by attrition in that Sephy can't kill him and thusly must eventually lose. Hell, knowing Ganondorf he'd probably just manipulate sephiroth into doing his bidding for him.