Here is the full list of all 26 Othercide achievements.
Activate all Remembrances
Defeat every boss in a single recollection
Have a level 15 Daughter
Defeat Suffering
Discover all story chapters
Defeat The Child
A Scythedancer has been germinated
Defeat The Maid
Defeat The Deacon
Finish the tutorial by defeating all enemies
Kill 300 enemies
Spend 4000 vitae
Defeat The Surgeon
Earn 5 traits on the same Daughter
Close 20 Synapses
Lose 400 HP because of reaction or interruption skills
Sacrifice a Daughter with one memory attached
Add one memory to a Daughter
Sacrifice a Bright Soul
Resurrect one Daughter
Start a new Recollection
Save a Bright Soul
A Daughter is killed in battle
Sacrifice a Daughter
Close the first Synapse
Reach the chrono map