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