Very easy achievement, load up any level and continue through it until you find a hole, a pit with spikes or something that would result in an instant death if you fell in it. Once there turn on your second controller and press A to select any character. He will spawn next to you. Whoever wants the achievement, use that player, face the other player and press B to grab them and throw them into the hole and that’s your achievement. I did it on level 2 like 10 seconds into the level.