Here is the full list of all 31 Princess.Loot.Pixel.Again x2 achievements.
Find glory
Complete Warrior missions
Find the grail
Kill rats
Beat Dark Warrior mission
Beat Dark Thief mission
Kill traitor
Complete Thief missions
Theft golden dagger
Theft crown
Save Princess
Complete Paladin missions
Kill a dragon
Save a cat
Find Mush and Flower
Find Fez hat, Meat cube and Scarf
Complete level without damage
Blink!
Beat Dark Paladin mission
Beat the boss
Find the Guitar
Find Crying baby
Collect 99 coins
Kill boss without damage
Steal coins
Dead first time
HA HA HA!
Find secret place
You are serious??