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