Here is the full list of all 24 Princess.Loot.Pixel.Again achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Collect 15 artifacts in one run
Get Rank C
Collect 46 artifacts
Make four deals with the cat in one run
Collect 3000G in one run
Archer saves King
Paladin saves King
Berserk saves King
Mage saves King
Necromancer saves King
Collect 23 artifacts
Rogue saves King
Make a party!
Get Rank S
Candlevania!
Press TAB in the main menu
Warrior saves King
Find baby
Get Rank A
Explode the door
Die for the first time
Get Rank B
Find hidden place
Start main Quest