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