If you could go back in time and stop one event from happening,what would it be ?

If you could go back in time and stop one event from happening, whether it be in ur life or someine else's life or a worldly event, what would it be and why?

I would have loved to have prevented the holocaust so so many people and families didnt have to suffer, but in reality if we could change it, what would our history be and would we have learned the lessons we did back then ?

I think we'd all like to change the war or Hitler being born, but it would have all sorts of repercussions and who's to say someone more evil wouldn't just have come along later? xxx