Here is the full list of all 40 Sniper Ghost Warrior Contracts achievements. It takes around 25-30 hours to unlock all of the achievements on Windows.
Kill 3 Enemies with 1 bullet
Unlock 10 Sniper Rifles
Kill enemy from each sniper rifle
Complete SIBIRSKAYA-7 JUNCTION Region on the highest difficulty
Buy 57 skills
Complete SIBIRSKAYA-7 JUNCTION Region
Complete 24 Contracts
Complete 9 of the Bounties
Unlock 14 Gadgets
Unlock 7 Sidearms
Complete 24 Challenges
Complete ARAKCHEYEV FORTRESS Region on the highest difficulty
Complete ARAKCHEYEV FORTRESS Region
Unlock 5 Regions
Complete BEKETOV VALLEY Region on the highest difficulty
Complete 13 of Challenges
Complete BEKETOV VALLEY Region
Complete 5 of the Bounties
Complete 13 Contracts
Eliminate Main Target when in the vechicle with the Mine
Find 14 collectibles
Eliminate Main Target with The Chain kill
Exfiltrate in under 1 minute after killing Igor Sekhov
Eliminate Main Target with Death from above
Kill enemy from zip line
Eliminate Main Target with Remote Sniper Turret
Complete KOLCHAK HARBOR Region on the highest difficulty
Buy 28 skills
Kill an Enemy from a 500 meters distance.
Complete KOLCHAK HARBOR Region
Find 7 of collectibles
Interrogate an Officer
Buy your first skill
Complete ALTAI MOUNTAINS Region on the highest difficulty
Complete ALTAI MOUNTAINS Region
Kill 80 enemies in single mission
Complete first Bounty
Complete first Challenge
Find the first collectible
Complete first Contract