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