Here is the full list of all 13 DeathSpank: Thongs of Virtue achievements.
Kill 3000 Enemies
Reach Level 20
Kill the Taking Tree
Discover all 44 Teleporting Outhouses
Watch Both Game Endings
Kill Santa Claus
Get an Engineering Degree
Go Sailing in a Pirate Ship
Kill Wortten
Learn to Speak Japanese
See all 20 of Madame Primp's Outfits
Kill the Evil Nun
Convince an Orque Guard you are an Orque