Here is the full list of all 12 DeathSpank achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Drink 50 Potions
Kill Lord Von Prong
Complete 6 Spelunker Quests
Destroy all 3 Queen Greems
Discover all 30 Teleporting Outhouses
Reach Level 20
Kill 2500 Enemies
Finish 50 Side Quests
Kill Sergeant Orque
Resurrect at an Outhouse
Kill 100 Chickens
Dispense the Good, Vanquish the Evil