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