Can be done with only two controllers.
Start a game of Deathmatch with no time limit, the highest score you can, and Phase Beam as the default weapon. Bring player 2 over to player 1, wait there long enough to give yourself enough time to get to that spot a second time (20 seconds should be more than enough) and destroy player 2. Move player 2 to that spot again, and destroy player 2 - along with their Mimic - in a single shot. Repeat another 24 times for your achievement.