Here is the full list of all 27 The Last DeadEnd achievements.
Positive ending was chosen
Last enemy was defeated
All wall texts were read on "Maiden Tower" level
Dark sinner was defeated
Many enemies were killed by explosion
Cyclop was defeated
10 enemies were killed by Nagant
Killing via auxiliary subject
Nagant found
Drudj was defeated
Gulyabani was defeated
10 enemies were killed by Axe
50 headshots were made
All wall texts were read on "Shirvanshahs' bath houses" level
10 headshots were made
10 enemies were killed by Makarov
Shotgun found
Bad ending was chosen
The whole encyclopedia became available
10 enemies were killed by Shotgun
10 enemies were killed by Sword
100 headshots were made
All wall texts were read on "Alleys of Old City" level
All wall texts were read on "Catacombs" level
All wall texts were read on "Sabail Castle" level
All wall texts were read on "Streets of Old City" level
All wall texts were read on "Road to the Maiden Tower" level