Here is the full list of all 28 Vampyr achievements. It takes around 35-40 hours to unlock all of the achievements on Windows.
Find all off-hand weapons
Find all ranged weapons
Find all melee weapons
Gather all collectibles
Save this poor plant with water
Find the recollection of Paulus Aurelianus
Turn all districts to hostile status
Embrace Clay during your first meeting with him
Turn a district to hostile status
Complete the game
Finish the game without killing any citizens
Defeat The Disaster
Take care of Swansea's fate
Defeat McCullum
Take care of Aloysius's fate
Defeat Doris
Upgrade a weapon to level 5
Defeat Mary
Take care of Sean's fate
Defeat Fergal
Heal 10 citizens
Take care of Dorothy's fate
Upgrade a weapon with a module
Upgrade a weapon
Eat 10 rats
Let Clay live during your first meeting with him
Take a ride with Doctor Swansea
Go to the Shelter and rest …