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