Knockout City

Trash chutes are the chutes located on the red raised areas outside of the middle of the Galaxy Burger map (see video). Simply jump down the shoot to unlock the achievement (although sometimes you have to do multiple times for the game to register). The video also shows a way to get another achievement at the same time for finishing an enemy in the trash shoot.

Of note, the achievements in this game occasionally do not register and take multiple tries. Also, some game modes a friend and I tried, like private and diamond dash, did not unlock the achievement for us and we only were able to get it on Team KO game mode.