Storm the common room and kill everyone without taking damage on Veteran. [Gold / 100G]
Mission 11: Atlas Falls
This trophy is extremely easy, don’t let the veteran difficulty fool you. After using the grappel gun you will have to kill a bunch of enemies and come to the common room. You will now have to breach the door (part of the story, cannot be missed). Breach it and throw all of your flashbangs and frag grenades to kill everyone inside. Don’t waste any grenades before reaching this room. You’ll need every single one. If you don’t kill all enemies with your grenades, then let your teammates do the rest. They will also kill enemies for you and cannot die. If you are being hit, restart the checkpoint.
Keep in mind that you have to play on veteran difficulty to unlock this trophy or achievement. Veteran difficulty is available from the beginning on and you can change the difficulty settings via mission select.