Inflated ego.
This one guy I knew thought he was complete bad ass. I won't go into the details now, but he provoked me and I still maintain that he got what he deserved. But anyways back to the point of the thread, said guy thought he would handle me, he ended up on the ground with me stomping on and kicking him. He got overconfident. Of course I fed his ego a bit, and got him overconfident once he had provoked me, but it worked. I got him to be too bold and destroyed him.
We've both apologized since, and talking to him he'd had about half a dozen karate lessons when he was a kid, and he thought from those and a self defense class that he could basically wail on anyone. Truth is he probably would be ready for the average person, as the majority of people you see on any given day have no idea how to fight.
