Here is the full list of all 52 Delve achievements.
Defeat Stagnas.
Defeat Heft.
Defeat The Dryadic Scion.
Defeat Budgeli.
Defeat Agrus.
Defeat the Queen of Diamonds.
Defeat the Queen of Spades.
Defeat the Queen of Clubs.
Defeat the Queen of Hearts.
Defeat the first Killer.
Defeat the second Killer.
Defeat the third Killer.
Defeat your Killer.
Traverse the Upper Layer.
Traverse the Middle Layer.
Traverse the Bottom Layer.
Recruit the Star.
Recruit Temperance.
Recruit the High Princess.
Recruit the Chariot.
Recruit Justice.
Recruit the Empress.
Recruit Strength.
Recruit the Fool.
Become a patron of the arts.
Make peace with Dryad.
Find the forest's secret.
Enter the BABEL labyrinth.
Learn the Hopeful Recollection.
Reclaim the Blacksmith's Ember.
Steal a Jewel.
Annoy the Aristocrat.
Locate and defeat Eloiskol.
Locate and defeat Improblex the Untraceable.
Apocalypse Ending.
Beach Ending.
Assimilation Ending
Extermination Ending.
Rampage Ending.
Peaceful Ending.
Escape Ending.
Regret Ending.
Betrayal Ending.
Victory Ending.
Defeat Ending.
Safe Ending.
Diplomacy Ending.
Autocracy Ending.
Hidden Ending.
True Ending.