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