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