... Everything? When Mikoto would fight Reisi, Reisi's sword would just not hurt his fists. There was a Strain once, who would punch things, and suddenly there's a neat hole in it, and when he punched Mikoto, nothing happened. Same thing with the strain who would jump really quick, his sword would start heating up but not hurt Mikoto's hand.

[ If Rise can't guess, Mikoto was a Red King. And Anna hasn't done much fighting. ]