Nothing less than 100% proof the Christian God exists. And it's funny reading all of these internet-tough guy responses that even if God was proven to exist they still wouldn't worship him. Would it be the "right" thing to do seeing as God tends to be a humongous wang? No, but if it was proven not worshipping him would land you an eternity in the kind of torment you literally cannot comprehend, and worshipping him would land you an eternity of happiness, you would have to actually be fundamentally retarded to not worship him. As incomprehensibly stupid as the incomprehensible pain you'd be feeling in hell.