Full list of all 82 Gears of War 3 achievements worth 2,000 gamerscore. It takes around 1000 hours to unlock all of the achievements in the base game.
The base game contains 50 achievements worth 1,000 Gamerscore, and there are 7 DLC packs containing 32 achievements worth 1,000 Gamerscore.
Earned the Onyx "War Supporter" medal.
Completed one match in all six Versus multiplayer modes.
Maxed the Consecutive Match Bonus in Versus multiplayer.
Earned the Bronze "Force Multiplier" medal.
Recovered all 42 Collectibles.
Completed all campaign Acts on Hardcore Difficulty.
Completed all campaign Acts on Insane Difficulty.
Earned the Silver "Number 1" medal.
Recovered all 15 COG Tags.
Reached level 50.
Executed your enemies with variety and style.
Reached level 25.
Earned an Onyx medal.
Earned the Bronze "Loot Courtesan" medal.
Completed 5 Arcade Campaign chapters in co-op.
Recovered 20 of 42 Collectibles.
Reached level 15.
Survived all 50 waves of Horde.
Wreaked vengence upon humanity!
Completed all campaign Acts on Casual or Normal Difficulty.
Complete all Acts in Co-op on any difficulty.
Complete all Acts in 4 player Co-op on any difficulty.
Killed Myrrah.
Rescued Adam Fenix from captivity.
Turned off the Maelstrom device.
Reached level 10.
Passed under the Maelstrom and found Azura.
Launched the sub.
Survived the first 10 waves of Horde.
Killed 10 enemies in Team Deathmatch.
Executed an infected player and is now turning Lambent.
Completed the first 12 waves of Beast.
Found enough fuel to get to Endeavor naval base.
Found and activated the fuel pump.
Drove from Anvil Gate to Mercy.
Reached level 5.
Defeated the Lambent Berserker.
Defended Anvil Gate from the Locust siege.
Arrived safely, kinda, at Anvil Gate.
Grabbed a Locust Gas Barge to travel to Anvil Gate.
Discovered the location of Adam Fenix.
Recovered 5 of 42 Collectibles.
Blew up the Lambent Leviathan from the bridge.
Defended and escaped from Cougar Stadium.
Found food and ammo in Hanover.
Defended the Raven's Nest from Lambent Leviathan.
Woke up from a bad dream.
Your skill and experience means you’re ready for Standard Versus multiplayer.
Secret.
Reach level 100 and earn every Onyx medal.
Found new places to destroy all humans.
We are the elite Onyx Guard!
Showed your friends the Horde Command Pack sights.
The Hammer of Dawn is now online!
Get 500 Silverback rocket kills in Horde (any map, any difficulty).
Ignored all Loader safety guidelines and killed 10 Locusts.
Completed "RAAM's Shadow" in 4 player co-op.
Showed 50 Locusts the meaning of sky-fire with HOD Command Center.
Completed "RAAM's Shadow" in Standard Campaign.
Completed "RAAM's Shadow" in Arcade Campaign.
As RAAM, ripped 50 Gears to shreds with your Kryll.
As Mauler, kill 10 Gears by reflecting their bullets using your shield.
Play 10 matches of Versus as a member of Zeta (Barrick, Tai, Minh, or Valera)(Standard or Casual).
As RAAM, execute Minh 10 times in Versus MP (Standard or Casual).
Defeated the first 10 waves of Horde with every member of Zeta in your party.
Level 100 and going back for more!
Completed all 50 waves of Horde on any of the Fenix Rising maps.
Completed all 12 waves of Beast on all Fenix Rising maps.
Won a Versus multiplayer match as a team of five Savage Marauders (any mode).
Won a Versus multiplayer match as a team of five Recruit Claytons (any mode).
Achieve level 100 a second time and choose to re-up for another tour.
Earn at least one of each of the original 132 combat ribbons.
Captured and "released" 20 opponents as the Savage Hunter.
Maxed out all of the Horde fortifications.
Still standing after 20 waves - you're a natural!
Found the right man for the job!
Completed all 12 waves of Beast on all Forces of Nature maps.
Complete all 50 waves of Horde on any of the Forces of Nature maps.
Get 25 kills with any of the hidden elementally charged Cleavers in Horde.
Win a match of Guardian on all Forces of Nature maps.
Kill 10 opponents as the leader in a round of Guardian on a Forces of Nature map.
Kill a Lambent Berserker with a team comprised of 5 Forces of Nature characters in Horde.