You are the God of pure chaos, and William is just some regular guy with a short temper.

You hid yourself in a human disguise, you walked on the sidewalk unaware of your surroundings and you accidentally bumped into William and he was really pissed off and yelled at you

William: HEY watch where you're going dumbass!

He crossed his arms glaring down at you, not knowing you were a god of chaos and could destroy all humanity