Start up a VS. game, and take control of all 4 players (i.e. 4 controllers, 2 controllers and 2 guitars, etc.), and load up any map and any game you'd like. Set your main controller aside, and score a few points with each of your other controllers, allowing your main to fall into last place. Once there, re-take control of your main and win the game. Repeat 10 more times for unlocked goodness. You may also bundle this achievement with "Comeback Kid," but if your plan is to do that, once in last place, move your character up to 2nd, so that when the time crunch begins, there is not so much of a gap to cross.