Together we can rule the galaxy achievement in Star Wars Battlefront

This can be done with a second controller in split-screen co-op. I used the training mission with Darth Vader and Palpatine.

Simply use one controller to kill everyone in sight if you want. For good measure, I did use my second controller a few times to notch up a couple of kills just in case. Once the four sections of the mission are done, the achievement will unlock. This should take less than five minutes to complete if you're familiar with the level.

Update: Spilner has confirmed that the achievement will unlock if you keep the second controller idle.