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