Full list of all 50 Marvel's Avengers achievements worth 1,000 gamerscore. It takes around 80-100 hours to unlock all of the achievements on Xbox One.
Complete 30 War Zones at Challenge III or higher rating
Reach Power Level 150 with any Hero
Rescue 100 AIM prisoners
Fully upgrade a major artifact
Earn a 100% rating on a mission without any team member being downed
Complete 15 Villain Sectors
Collect 50 intelligence files
Complete an Elite Heroic Hive
Reach Faction Rank 25 in any faction
Complete the "Iconic Avengers" mission chain
Earn a total of 250 Hero Levels across the entire Hero Roster
Complete 100 assignments
Complete five Hive missions
Collect 500 gear items
Reach Hero Level 50 and purchase all Skills for any Hero
Complete the "A Global Offensive" mission chain
Break into 30 Depots
Open 100 strongboxes
Complete HARM Challenges I to V
Defeat MODOK and the Kree
Reunite the Avengers
Complete any mission in under three minutes
Defeat 50 enemies with Assault Heroic or Ultimate Heroic abilities
Complete 10 assignments
Collect three Artifacts
Equip all Legendary or better gear with any hero
Earn a 100% rating for any War Zone at Challenge IV rating
Reach Hero Level 5 with five different Heroes
Rescue Captain America
Reach the AIM space station
Stop the Helicarrier from crashing into New York City
Rescue Inhumans from the research facility
Recruit Black Widow
Purchase an item from two different faction vendors
Locate the Ant Hill
Destroy the AIM arc reactor
Collect 20 different enemy codex files
Recruit Tony Stark
Earn a five star rating on an objective without any team member taking damage
Recover the SHIELD Protocols
Fully upgrade any gear item
Reach a combo of 20 hits or higher
Recruit Bruce Banner
Discover the location of the Chimera
Escape the clutches of AIM in New Jersey
Defeat 10 or more enemies with a single Heroic ability activation
Reach the VIP balcony
Collect a full comic set
Open 50 Cache strongboxes
Complete 50 Hive missions