Here is the full list of all 26 Serious Sam VR: The First Encounter achievements.
Complete a level in co-op with blood option set to hippy.
Complete any level in co-op.
Complete the game.
Complete the game in single player by beating the estimated time on each level.
Trigger Ugh-Zan's regeneration.
Leap into the unknown on Luxor.
Defeat the Lava Golem boss.
Pull out a single Colt and immediately deliver a killing shot.
Kill 300 Enemies with the Minigun.
Kill 150 Enemies with the Rocket Launcher.
Kill 100 Enemies with the Cannon.
Pierce at least 10 enemies with a single cannonball.
Kill 20 enemies with the Minigun without releasing the trigger.
Find at least 10 secrets in single player.
Obtain the Water Element.
Kill 200 Enemies with the Thompson Submachine gun.
Obtain the Fire Element.
Kill 250 Enemies with a shotgun.
Obtain the Earth Element.
Obtain the Air Element.
Complete any level in single player.
Complete the Metropolis level in single player on unmodified serious difficulty.
Complete the game in single player on unmodified serious difficulty.
Complete the game in co-op on unmodified serious difficulty.
Win a versus match.
Frag a total of 100 players.