He's been touched by the fist of Zeus.
When I was sparring and all that stuff, I used to train against someone like TS described. Taller than me, but much lighter, and he hit with the force of a horny gorilla, he banged the shit out of my head. His punches were controlled, and they were so well placed, his range was perfect. Even though he controlled his punches, they still hurt like fuck. Just because someone is a skinny lanky steak of piss, doesn't mean that they can't knock you flat on your ass because you're a "bigger" guy.
But once we hit the floor I dry humped the fuck out of him.
Edit. Moral of the story, technique and repetition will increase punching power.