Here is the full list of all 28 Serious Sam VR: The Second Encounter achievements.
Complete any level in single player.
Use the Flamethrower on a Lava Golem.
Cut down some trees.
Find a secret under water.
Destroy an enemy cannon with your own cannon.
Survive the storm on the Grand Cathedral.
Kill 50 Cucurbitos.
Kill 10 enemies with the Chainsaw without releasing the trigger.
Kill 20 enemies with the Minigun without releasing the trigger.
Kill at least 30 enemies with a single Serious Bomb.
Find at least 10 secrets in single player.
Burn 100 enemies to death.
Kill 100 enemies with Serious Damage active.
Kill 100 Kleers with the Cannon.
Kill 20 Harpies with the Sniper rifle.
Kill 200 enemies with the Laser gun.
Complete the game.
Complete the game in single player by beating the estimated time on each level.
Complete the game in single player on unmodified serious difficulty.
Complete any level in co-op.
Complete the South America episode in single player or cooperative.
Complete the Persia episode in single player or cooperative.
Complete the Medieval episode in single player or cooperative.
Earn a gold medal on any level in cooperative Survival.
Earn a gold medal on any level in single player Survival.
Win a versus match.
Frag a total of 100 players.
Finish the Legend of the Beast campaign in single player or cooperative.