Full list of all 26 Alekhine's Gun achievements worth 1,000 gamerscore. It takes around 12-15 hours to unlock all of the achievements on Xbox One.
Use Chloroform on 30 enemies
Hide 30 bodies
Garrote 30 enemies
Level 11 Completed
Level 10 Completed
Level 9 Completed
Level 8 Completed
Level 7 Completed
Level 6 Completed
Level 5 Completed
Perfect lockpicking attempt
Get 30 Headshots
Level 4 Completed
Level 3 Completed
Perform a perfect rewiring (sabotage minigame)
Level 2 Completed
Complete a level using one disguise or less
Complete a level without using instinct mode
Level 1 Completed
Complete all assassinations in a level using only accidents
Complete a Level without Killing (except for assassination targets)
Obtain Ghost Ranking on a level
Complete a level without using your gun
Obtain all disguises in the game
Complete game without killing (except for assassination targets)
Obtain Maniac Ranking on a level