Here is the full list of all 24 Sniper: Ghost Warrior achievements.
Kill 2000 enemies. (Multiplayer)
Win 50 rounds playing online. (Multiplayer)
Kill 250 people using pistol. (Multiplayer)
Kill 500 people using sniper rifle. (Multiplayer)
Kill 250 people using sniper rifle. (Multiplayer)
Complete Act 4.
Finish the game on Easy difficulty.
Finish the game on Normal difficulty.
Finish the game on Hard difficulty.
Complete Act 3.
Kill a total of 30 enemies with Browning gun.
Complete Act 2.
Collect all secrets.
Shoot 5 cable lines using sniper rifles.
Kill all enemies attacking your pontoon from the riverside on 'Weaken The Regime' level.
Complete Act 1.
Kill 2 enemy with one grenade.
Kill 2 enemy with one shot.
Shoot an enemy through a wall.
Kill 10 enemies with throwing knives.
Kill 10 birds.
Kill 15 enemy using concentration mode.
Deliver 50 headshots.
Deliver 100 headshots.