Very easy to achieve but as with all the achievements in this DLC the trick is ensuring the challenge is equipped at the start without this, the achievement will not unlock!
Once you've ensured you've started a round with the challenge equipped run around until you either find a cave with a trap or enemies and let the other player you're with get downed. Then all you have to do is interact with them once you're close enough and the coast is clear. Should be very easy early on with the low level enemies that are easy to kill to let them down one player safely and then kill them off.