Take for instance you are able to go back in time and have one of the worst leaders in history killed him/ her before they came into power, thus eliminating the atrocities they committed. Or see atrocities being committed, kill them to stop them. The fact that you did this evil thing (killing) becomes a good thing.
On the other hand can something be so overwhelmingly good/ perfect, but implemented or enacted in such a way that it is evil?
At day's end are these labels of good and evil just manifestations of our own viewpoint? How do we know the difference?