Not unbeatable but damn good. If he can be the Khan that boxed circles around Mallinaggi, that is a serious dude to reckon with. He also does not have a glass chin. he took punishing shots from guys like Maidana and didn't leave his feet, and Garcia's left hook is trouble for anyone.
No one is unbeatable, some just look that way because they avoid the biggest challenges or happen to be in a particularly weak era.