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
Kill 2500 Enemies
Reach Level 20
Discover all 30 Teleporting Outhouses
Kill Sergeant Orque
Destroy all 3 Queen Greems
Complete 6 Spelunker Quests
Finish 50 Side Quests
Resurrect at an Outhouse
Kill 100 Chickens