Here is the full list of all 56 Gears of War: Ultimate Edition achievements worth 1,250 gamerscore.
Recovered all 33 COG tags
Defeated General RAAM
Completed all acts on Casual Difficulty
Completed all acts on Normal Difficulty
Completed all acts on Hardcore Difficulty
Completed all acts on Insane Difficulty
Completed all acts in co-op
Defeated General RAAM in co-op on Insane without either player being DBNO
Boarded the Imulsion bound train with the Lightmass Bomb
Killed the Brumak
Closed all 4 e-holes around the fountain in Fish in a Barrel without any Locust fully emerging
Restored communications with Control
Killed an enemy with every weapon in Versus
Reached level 25
Won 10 Versus matches without losing a round
Finished with the highest points in a Versus match
Restored power to the bridge
Escaped from the Brumak (end of Ch.6)
Discovered Adam's secret lab
Killed a Berserker in the Conservatory
Delta found downed chopper
Won a match in every Versus game type
Deployed the Sonic Resonator
Killed a Corpser
Recovered 22 COG tags
Delta descended into the mines
Reached level 10
Reunited with Baird and Cole inside the Imulsion Factory
Killed 3 enemies at once 10 different times
Defended Stranded Settlement and headed to Lethia Imulsion Factory
Got the Junker at Chap's gas station
Read one full comic
Completed 10 different chapters in co-op
Used the spotlight as protection from the Kryll
Made a Deal with Franklin
Recovered 11 COG tags
Killed the Berserker in the Tomb of the Unknown
Rescued Damon Baird from the Tomb of the Unknown
Rescued Augustus Cole in the House of Sovereigns
Completed 1 co-op chapter in co-op
Escaped from the Slab
Completed tutorial path on any difficulty
Reached level 5
Performed 25 perfect active reloads
Performed 5 perfect active reloads in a row
Played one Versus Match with a Custom Weapon Skin
Finished playing a Versus match
Spot 100 enemies ending in a kill in Versus (social or competitive)
Revive 100 teammates in Versus multiplayer (social or competitive)
Win a match in every Versus map (social or competitive)
Kill 10,000 people in Versus matches
Complete 100 matches in ring-based game types on Xbox Live and capture 3 objectives in each match
Win 20 rounds in ring-based game types on Xbox Live by shutting out the opposing team
Win 25 matches in Boxes (social or competitive)
Reach level 100 and re-up
Win 25 matches in Team Deathmatch