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