Hannibal.
If you think about it with Jigsaw and his "mission" to make people realize how life is worth living after all, has he really helped someone achieve that? Only one person has actually survived his traps, Amanda, and even then I'd argue that she didn't really take the lesson to heart.. if she had, she would have passed it along instead of being a spiteful bitch. (I'm not going to count people who weren't actually involved in the games, like that little kid from the 2nd movie, because he didn't have to actually work for his life.
Hanniball, though, he has no pretensions about saving people. He knows that that's a large amount of BS, and so just eats those little shits up.