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