Bleach Manga thread (SPOILERS)

There must be limits to it that he hasn't stated himself. After all, why would you publicly state your own weaknesses? If he can quite literally alter ANYTHING'S past to ANYTHING he wanted, the second he cut Byakuya he could have altered his past so that he had a terminal illness or something and thus was already dead. Makes sense, no?

Point taken. I think his power is that he inserts himself into the target's past, not that he changes the target itself. So I'm assuming he can't alter your DNA or body to kill you with illness or just kill you in the past. If he could, he'd basically be a god of space/time.