For me, it's not just the power. It's that he is equally skilled with his left and his right to the head and to the body. Dude is freakin' scary.
His combination of power and technique. The fact he can take you out with either hand with any punch to head or body is rare. He's stopped probably as many people with body shots as head shots, something you don't really see. I also like the fact he does his talking in the ring. He's polite and courteous outside the ring but a ruthless assassin inside the ring.
What strikes me about this video is that his opponents look like they are in such pain when he hits them with both head and body shots.