...into the fire.G 30

To unlock this achievement you simply need to save one of your buddies from death. It can be done on any APR or UFLL mission as long as you follow the subverting mission path (follow the blue marker after the phone call once you accept the initial faction mission). This will guarantee playing through the mission with a buddy. Wait for you buddy to be injured during the mission. Once he is down run up to him, press Y to help him and then RT to administer a shot to regain their health.