What evidence would you need to see to actually believe there was a higher power?(While living)

I just posted a question asking "how anyone could be certain of the lack of a higher power while possessing such little knowledge of our universe." Then got the, "You can't prove a negative, so you need a proof of positive" and that did stump me. So made me think what would really convince you of the existence of a deity or supreme being? Jesus coming back? A holy war? Some crazy as miracle?