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
Collect 46 artifacts
Necromancer saves King
Berserk saves King
Mage saves King
Rogue saves King
Make four deals with the cat in one run
Press TAB in the main menu
Archer saves King
Paladin saves King
Candlevania!
Explode the door
Collect 23 artifacts
Warrior saves King
Get Rank S
Get Rank A
Die for the first time
Find baby
Get Rank B
Find hidden place
Start main Quest
Get Rank C
Make a party!
Collect 3000G in one run