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