God wanted a perfect world, so he decided to flood the entire planet and drown everyone but Noah and his family. Apparently God at that time was unaware that he was omnipotent, and could have just wiped out humans with a virus.
And get this: God is omniscient and knows the future, so at the moment he destroyed almost the entire population of the Earth, he knew it was never going to work.
Hitler wanted a perfect Europe and he decided to wipe out all the Jews. He failed, of course.
The main difference between God and Hitler seems to be that Hitler was not omniscient.
I think that perhaps most of us know who the demented idiot is.