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