Full list of all 57 Gears of War achievements worth 1,250 gamerscore. It takes around 150-200 hours to unlock all of the achievements in the base game.
The base game contains 49 achievements worth 1,000 Gamerscore, and there are 2 DLC packs containing 8 achievements worth 250 Gamerscore.
Recover all of the COG tags (on any difficulty)
Complete all acts in co-op as Dominic Santiago on any difficulty
Complete Act 3 on Insane Difficulty
Complete all acts on Insane Difficulty
Revive 100 teammates in ranked matches
Complete Act 4 on Insane Difficulty
Kill 3 enemies at once 10 different times (on any difficulty)
Kill 100 enemies in ranked matches with a headshot
Kill 100 enemies in ranked matches with the Hammer of Dawn
Complete Act 2 on Insane Difficulty
Kill 100 enemies in ranked matches with the Longshot
Complete Act 5 on Insane Difficulty
Kill 100 enemies in ranked matches with a pistol
Complete Act 5 on Hardcore Difficulty
Complete all acts on Hardcore Difficulty
Complete Act 4 on Hardcore Difficulty
Kill 100 enemies in ranked matches with the Torque Bow
Kill 100 enemies in ranked matches with an execution
Complete Act 1 on Insane Difficulty
Kill 100 enemies in ranked matches with the curb stomp
Kill 100 enemies in ranked matches with the Boomshot
Recover two-thirds of the COG tags (on any difficulty)
Complete Act 3 on Hardcore Difficulty
Host and complete 50 ranked matches
Defeat General RAAM on Hardcore Difficulty
Defeat a Corpser on Hardcore Difficulty
Kill 100 enemies in ranked matches with grenade tag
Kill 100 enemies in ranked matches with the Chainsaw
Complete Act 2 on Hardcore Difficulty
Complete 10 different co-op chapters as Dominic Santiago on any difficulty
Win a ranked match on every versus map
Win 10 ranked matches without losing a round
Win a ranked match in every versus game type
Finish with the highest points in a ranked match
Complete Act 1 on Hardcore Difficulty
Defeat a Berserker on Hardcore Difficulty
Recover one-third of the COG tags (on any difficulty)
Complete 1 co-op chapter as Dominic Santiago on any difficulty
Complete Act 5 on Casual Difficulty
Complete all acts on Casual Difficulty
Complete Act 4 on Casual Difficulty
Complete Act 3 on Casual Difficulty
Perform 5 perfect active reloads in a row (on any difficulty)
Perform 25 perfect active reloads (on any difficulty)
Complete Act 2 on Casual Difficulty
Finish playing a versus ranked match
Complete Act 1 on Casual Difficulty
Completed tutorial level on any skill level
Kill 10,000 people in versus ranked match total
Win 20 multiplayer matches of 3+ rounds in any game type on the Process multiplayer map
Win 20 multiplayer matches of 3+ rounds in any game type on the Garden multiplayer map
Win 20 multiplayer matches of 3+ rounds in any game type on the Bullet Marsh multiplayer map
Win 20 multiplayer matches of 3+ rounds in any game type on the Subway multiplayer map
Win a multiplayer match of 3+ rounds in any game type on 6 different downloadable maps
Complete 100 multiplayer matches of 3+ rounds in Annex and capture 3 objectives in each match
Win 20 rounds of multiplayer matches in Annex by fewer than 5 points
Win 20 rounds of multiplayer matches in Annex by shutting out the opposing team