I'm going to snap at a classmate
Why will you snap at a classmate?
He always smells of pee and brought the smell to the room
If you think his hygiene is a problem, you can talk to him more rationally. Snapping at him will only make the situation worse and could hurt his feelings.
I have a better idea. I will tell the whole class what I think of him.
You could really hurt his feelings you know. You should tell him privately, you really don't know his situation. He might not have parents who care at home or they could be really poor.