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