I remember one of the young female brown belts (about 125 pounds) I used to train with dealing with a 300 pound male newbie uke. I was teaching nikkajo (nikkyo) and warned him to be carefull of his wrist, as in take the ukemi. He started being a jerk (looking around the room smirking, shoving her around, etc.), so she floored him.
It was quite illuminating.
He paid much more attention to his wrist, his partner, and the class after that. And we learned that the 'color' of nikkajo is 'red'...