BADLAND: Game of the Year Edition

The fastest method to complete this will require you to connect a second controller, and a lot of just tapping A. Enter the multiplayer menus, ready up and select any of the levels, although I used Explorers. Set the number of rounds to 99 (For some reason it doesn't let you set it to 100), and then just press A on both controllers to ready at each round, then just let them die by going off the side of the screen. Mash A through the next two score counters, and repeat. This should take around 10 minutes, and once you have completed them, simply load up another game with 1 round, use the same technique, and then your achievement will unlock.