South Park Tenormans Revenge

If you are playing the game online or split-screen, then complete all levels with 2 or more players.

If you are playing the game by yourself, you can use a second controller to get this achievement:
Play through the level as you normally would, then before exiting the level through the blue portal, join the game with a second controller by pressing the button. Complete the level and it will count towards this achievement.
See achievement ”Respect My Authoritah!” For a video on this method.

If you are playing this game solo, I recommend that you combine this achievement with the ”Respect My Authoritah!” achievement.

At the level select screen, press to see which levels that are completed in co-op.

Note: If you play with a friend on a level you haven't unlocked yet on your gamertag, you still get credit for completing it in co-op.