Here is the full list of all 28 Vampyr achievements. It takes around 40-50 hours to unlock all of the achievements on Windows.
Embrace Clay during your first meeting with him
Finish the game without killing any citizens
Complete the game
Defeat The Disaster
Save this poor plant with water
Turn a district to hostile status
Find the recollection of Paulus Aurelianus
Take care of Swansea's fate
Defeat McCullum
Take care of Aloysius's fate
Defeat Doris
Defeat Mary
Upgrade a weapon to level 5
Take care of Sean's fate
Defeat Fergal
Eat 10 rats
Take care of Dorothy's fate
Heal 10 citizens
Let Clay live during your first meeting with him
Take a ride with Doctor Swansea
Upgrade a weapon with a module
Upgrade a weapon
Go to the Shelter and rest …
Find all melee weapons
Find all ranged weapons
Find all off-hand weapons
Gather all collectibles
Turn all districts to hostile status