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