That's a much tougher order than you think it is. You'd have to go far enough in time to when humanity started (if it even has a set starting point; evolution's tricky like that), and find where the pre-people/first humans were, and kill them all. While avoiding getting killed from the environment before you somehow manage to find them. Any other way to make humanity go extinct is something you could probably have just as much luck doing now as in the past (ie: bringing back nuclear bombs; you could just nuke the world but good luck figuring out how).
I'm not even going to ask why...that sounds like bait to me.
I think I would sneak up and free Jesus off the cross.
I have no idea what effect that would have.
Still a better plan than mine. The best I could think of was to save the dinosaurs lol. Find out a way to prevent that mass extinction and see where that takes the world. Will it continue on it's path or will they still go extinct.The law at the time was that anyone put on a cross on the Friday morning would be taken down before the Sabbath started on the Friday evening instead of being left there for the days it took to die so it was never intended for him to die ...........
Still a better plan than mine. The best I could think of was to save the dinosaurs lol. Find out a way to prevent that mass extinction and see where that takes the world. Will it continue on it's path or will they still go extinct.
My thought about Jesus is that I would probably go back and Jesus would say to leave him there, then I'll be stuck with the choice of directly going against Jesus or following Jesus. The scenario gets depressing from there so I figure. Saving dinosaurs would be interesting. To see what becomes of it.