Why Guerrero hurt and dropped Berto and hurt Thurman In the 10th, I think Guerrero would maul Khan, and I'm not just saying that as a devout Khan hater.
If Guerrero comes to box, Khan wins. If Guerrero comes to fight, Guerrero wins. And of course there's the ever-present threat of Guerrero just finding that awful chin.
I think if I had to go off of who Khan CAN'T beat, no matter how hard he tries, no matter what he does, I would come up with: Floyd Manny Thurman Porter I see absolutely no way he gets through those guys. Fairly certain they all stop him, too.
I would only put Thurman and Manny from those 4, because both smash the chin, the other two probably can't.