Here is the full list of all 14 Hidden Deep achievements.
Kill 5 enemies in a row while hanging on the grappling hook
Kill 1000 monsters
Drill 100 meters of tunnel using the Tunnel Boring Machines
Kill the ceiling tentacle before it kills you on your first encounter
Ride a elevator from top to bottom non-stop. Yes, that's possible.
Complete a level with high enemy presence without dying (must be 50+ enemies)
Rappel down the full length of your grappling hook's line
Kill 100 monsters
Kill 20 enemies with your gun without dying
Let another team member use your rope to climb
Fall from 50 meters or more
Use the grappling hook as a zip-line
Kill 3 enemies using one Scan-Ball
Find a hidden cave using the Terra-Scanner