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