Defend the Couch
A simple violent game. One team must defend a couch (or a mattress or table), and the other team must conquer it.
The conquering team must pull the defending team away from the couch. As long as the defenders touch the couch its still being defended. When a defender no longer touches the couch they are out of the game.
The game end after a fixed time, or when no defender is touching the couch. The roles can then be inverted, and the game run again.
All the kids against the trainer. Set a time limit.