Use these settings for the achievement:
1 player worth of enemies
I find best to do solo, or with friends. I would not allow randoms because after rushing to the exit on wave 12, the randoms tend to continue trying to play, at this point you have to hope they go down and die so you can exit. Survive until wave 12, once you do this a section of the map opens up for players to escape through, all the remaining players must get in the white circle to escape, when the match finishes and the results screen appears the achievement will pop.