Do this Post Game so you don't void the No Child Left Behind trophy.
Post game, put Kenny in your party and go out into the woods for some battles with wild dogs. On your turn, select your melee weapon and attack, but don't press any buttons. You won't do any damage. On Kenny's turn, go to abilities and select Kenny's Furry Friends ability. The game will prompt you to shake the rats off, but don't press anything. Kenny will die. Kill the enemies to finish the battle. Rinse and repeat.
One of these 10 deaths can also be used while earning the Avengers trophy. See my guide here: