This is quite easy to do.
While every Minor Operation works for this it is easiest if you have downloaded the Codebreaker mission. It is short and doesn't have any difficult enemies.
Hit
to enter Battle Focus whenever you can and let your teammates do the majority of the work. If you don't feel like hanging back you can also get up close and personal with some of the aliens. When next to them press
to show them how great your fists work with their faces