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