Here is the full list of all 12 GUNGRAVE VR U.N achievements.
Completed the tutorial.
Cleared Stage 1.
Cleared Stage 2.
Cleared Stage 3.
Destroyed 50 objects.
Hit enemies 20 times with reflected projectiles.
Scored over 1000 headshots.
Used Demolition Shot 30 times.
Defeated 1,000 enemies with Cerberus.
Defeated 50 enemies with the Death Coffin.
Used Reaper Time for 444 seconds.
Earned SS score on normal difficulty for all stages.