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