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