Here is the full list of all 38 Sniper: Ghost Warrior 2 achievements. It takes around 25-30 hours to unlock all of the achievements on Windows.
Complete the game on Expert
Kill all enemy snipers in Sniper Alley without being hit ("Ghosts of Sarajevo")
Kill three or more enemies by shooting a grenade
Win 25 Team Deathmatch rounds
In one multiplayer round kill an opponent with a sniper rifle, sidearm and melee attack
Win 10 Team Deathmatch rounds
Take 50 headshots in multiplayer
Kill 100 opponents in multiplayer
Win 5 rounds in a row in Team Deathmatch
Take 25 headshots in multiplayer
Kill 10 opponents in multiplayer using your sidearm
Kill 50 opponents in multiplayer
Kill 25 opponents in multiplayer
Complete the game on Casual
Complete the Campaign using max one medkit per mission
Complete the game on Medium
Kill Maddox once and for all ("No Loose Ends")
In the final duel with Maddox, kill him with the first shot ("No Loose Ends")
Collect all secrets in Act 3
Retrieve your weapon without being detected ("Burning Bridges")
Complete Act 2
Collect all secrets in Act 2
Kill 30 enemies using your sidearm
Kill Major Vladic ("And Justice For All")
Kill 15 enemies with a stealth kill
Complete Act 1
Complete any act without using medkits
Collect all secrets in Act 1
Kill all enemies in the beach houses without causing an alarm ("Leave No Man Behind")
Participate in any multiplayer match
Complete any single player mission without using med kits, but taking damage
Kill 25 enemies using thermal or night vision goggles
Rescue the friendly ("From Out Of Nowhere")
Kill 20 enemies from a distance of 600m or greater
Take 50 headshots in single player
Take a successful shot from a distance of 1 km or greater
Achieve 100% accuracy in any single player mission
Kill 50 enemies while holding your breath