Pity Pit

If you're having problems with achievements not unlocking in this game, don't worry, it's a simple fix. Press the guide button and then select Pity Pit with the start button and close the game out. Now relaunch it, and once you select your profile you want to play the game as, the achievements will pop. I had roughly 1,500 gamerscore not unlock for me, and this did the trick. It may only unlock a few achievements at a time, but just keep doing this and they all will eventually pop.