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