During the second mission, when overloading mind control devices, run up to seven of the enemies and hit the melee button. There are enough enemies that you should be able to do this and “Pew! Pew! Pew!” in the same play through, but if you’re concerned just pick a segment of the mission, finish the melees, and then hit “Start,” “Retry or Exit Mission,” and restart from your check point to reuse all those enemies.