Former Fat Kid here. Still Fat. No longer Kid. Two bullies dealt with, one when the teacher left the room for a moment, he started with me, and I'd had enough and finished it. The other in a shorter amount of time when he (stupidly) started picking on me while he had a broken leg, on crutches... and I took those crutches and dropped them down the center of the stairwell, leaving him to scoot on his ass down from the 3rd floor to the basement. That one realized "Ah, shit, I'm at his mercy, aren't I?" Sometimes the pushback doesn't need to be too hard. Other times the pushback needs to be a total ass whomping. But we do need to push back.