I posted this on the old board, part of a "Heroes Behaving Badly" theme. John Byrne himself said in an interview he might have done the story with the three Kryptonians dead in another way, killing each other or something, and Superman wondering if he would have killed them.
It *seems* Infinite Crisis and other "Superboy Prime time punching" switched/nullified this. It curiously wasn't brought up after Wonder Woman killed Max Lord.