Here is the full list of all 40 Overlord: Fellowship of Evil achievements worth 1,000 gamerscore.
You completed a quest in local co-op.
You bought all statue upgrades for all characters.
You gained 100 crowns in-game.
You completed 100 traversal tasks within the time limit.
You fully upgraded all four minion colours.
You completed act 3.
The plot thickens.
You defeated Sparkle.
You defeated Clarisa.
You defeated Cedric.
You completed act 2.
Careful, we already lost one Overlord down there! I wonder what happened to him? - Gnarl
You defeated the Void Gazer.
You introduced the peasants to the zombies!
You completed act 1.
You bought all of one character's statue upgrades.
You fully upgraded one minion colour.
You bought half of one character's statue upgrades.
Your minions looted 250 shiny objects.
You killed 50 sheep
You crashed the banquet.
You completed the prologue.
Your Reds killed 100 enemies with their explosions. Boom!
Your Browns killed 50 enemies.
You knocked 20 enemies off the Netherdeep and into the Abyss!
You gained 100% of the crowns in one quest.
Your Greens assassinated 50 enemies
Your Blues healed 500 times.
You helped Ricket fix her forge.
You defeated the Trolls.
You summoned 500 minions.
You summoned 250 minions.
You had 12 or more minions active at a single moment.
You summoned 50 minions.
You completed the tutorial.
Obtain all weapons for all characters
With four players, each summon 4 minions at the same time.
Complete any quest in online multiplayer, with at least one other player
Kill a "boss enemy" in a multiplayer game.
Finish a quest in 1st place in multiplayer