Here is the full list of all 15 One More Dungeon achievements.
Сomplete the game with "Fog" or "Broken cartridge" mutator
Сomplete the game
Сomplete eight levels
Buy all the mutators
Finish the level in under 2 minutes
Squash 25 bugs
Put the items in all the inventory slots
Kill the Ancient Necromancer
Сomplete five levels
Die after drinking the poison
Kill the Elder Flower
Сomplete the first level
Start the game with any mutator
Сomplete the game with "No margin for error" or "Curse" mutator
Spend 50 coins