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