Full list of all 54 Overlord achievements worth 1,250 gamerscore. It takes around 40-50 hours to unlock all of the achievements in the base game on Xbox 360.
The base game contains 44 achievements worth 1,000 Gamerscore, and there are 2 DLC packs containing 10 achievements worth 250 Gamerscore.
You have retrieved the Tower Heart and powered up the Tower
You have started rebuilding the Tower
You have recovered the Food
You have harvested a few Minions
You punctured Melvin Underbelly
You have Red Minions!
You have the Steel Smelter
You have harvested a lot of Minions
You have a Mistress
You have Green Minions!
You have Blue Minions!
You have harvested a huge amount of Minions
You put Oberon to Sleep permanently
You cured Sir William's disease
You have the Durium Smelter
You have an Ultimately Imbued Durium Set
You have a full Durium set
You have defeated half the Dungeon Creatures
You ground-down Goldo and wrecked Rollie
You stole Jewel
You have the Arcanium Smelter
You and your Mistress have rocked the Dark Tower
Kahn made you very angry
Evil Overlord
You have an Ultimately Imbued Arcanium Set
You have a full Arcanium set
You have created the Ultimate Horde
You have defeated all Dungeon Creatures
You are the True Overlord
Really Evil Overlord
You have an Ultimately Imbued Steel Set
You have harvested a massive amount of Minions
You have collected all the Tower Objects
Last for 5 minutes in Survival
Last for 15 minutes in Survival
Last for 30 minutes in Survival
Complete a ranked Pillage match
Win a ranked Pillage match
Win 10 ranked Pillage matches
Win 50 ranked Pillage matches
Complete a ranked Slaughter match
Win a ranked Slaughter match
Win 10 ranked Slaughter matches
Win 50 ranked Slaughter matches
Defeat the 7th Hero in Legendary Mode
Last for 45 mins in a Expansion Survival Map
Win 25 ranked Expansion Pillage Maps
Win 25 ranked Expansion Slaughter matches
Defeat all the Expansion Dungeon Creatures
Conquer the Mellow Hills Abyss
Conquer the Evernight Forest Abyss
Conquer the Heavens Peak Abyss
Conquer the Golden Halls Abyss
Conquer the Ruborian Desert Abyss