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