I just wanted to say that all maps have been released, so you can get this now without any map exploits.
The maps you’ll need to complete are (in order of release):
- The Barracks
- The Choke
- Lethal Engagements
- The End
- Melee Brawl
- The Corruption
You can keep track of which maps you have completed, and on which difficulty under Stats > Escape > Completed maps.
Im Forever Dope suggests that there are progress issues with this achievement, so it could be a good idea to keep an eye on your achievement tracker and make sure that you actually get progress for completing a map.