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