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