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.
Necromancer saves King
Press TAB in the main menu
Berserk saves King
Collect 46 artifacts
Collect 23 artifacts
Make a party!
Collect 15 artifacts in one run
Make four deals with the cat in one run
Get Rank C
Archer saves King
Paladin saves King
Mage saves King
Rogue saves King
Collect 3000G in one run
Warrior saves King
Find baby
Candlevania!
Explode the door
Get Rank S
Get Rank A
Find hidden place
Get Rank B
Die for the first time
Start main Quest