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 won 50 ranked Pillage matches
You won 10 ranked Pillage matches
You won 50 ranked Slaughter matches
You won 10 ranked Slaughter matches
You have retrieved the Tower Heart and powered up the Tower
You have started rebuilding the Tower
You have a Mistress
You have recovered the Food
You punctured Melvin Underbelly
You have Red Minions!
You have Green Minions!
You have the Steel Smelter
You have harvested a few Minions
You have harvested a lot of Minions
You won a ranking Pillage match
You completed a ranked Pillage match
You won a ranking Slaughter match
You completed a ranked Slaughter match
You are the True Overlord
You have a full Durium set
Kahn made you very angry
You stole Jewel
You have a full Arcanium set
You ground-down Goldo and wrecked Rollie
You have the Arcanium Smelter
You put Oberon to Sleep permanently
You have the Durium Smelter
You and your Mistress have rocked the Dark Tower
You cured Sir William's disease
You have harvested a huge amount of Minions
You have Blue Minions!
Win with the blackest heart
Win with the clearest conscience
Forge an Ultimately Imbued Steel Set
Forge an Ultimately Imbued Durium Set
Forge an Ultimately Imbued Arcanium Set
Harvest a massive amount of Lifeforce
Collect all the Tower Objects
Get a full Horde, fully equipped
Defeat half the Dungeon Creatures
Defeat all the Dungeon Creatures
Last for 5 minutes in Survival
Last for 15 minutes in Survival
Last for 30 minutes in Survival
You won 25 ranked Expansion Pillage Maps
You won 25 ranked Expansion Slaughter matches
Defeat the 7th Hero in Legendary Mode
Last for 45 mins in a Expansion Survival Map
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