Full list of all 65 LEGO Marvel's Avengers achievements worth 1,250 gamerscore. It takes around 35-40 hours to unlock all of the achievements in the base game.
The base game contains 40 achievements worth 1,000 Gamerscore, and there are 5 DLC packs containing 25 achievements worth 250 Gamerscore.
Witnessed the 100% Stud Fountain inside Avengers Tower
Played as every Iron Man variant in one session
Played as Captain Britain, Union Jack, Spitfire, Agent Carter and Mandarin (Trevor Slattery)
Grew Ant-Man, Black Goliath, and Fin Fang Foom in one sitting
Played as: Hawkeye (Kate Bishop), Hulkling, Wiccan, America Chavez and Speed in the same session
Played as Moon Knight, Moondragon and Moon Boy in one session
Played as Iron Fist, Daredevil, Jewel (Jessica Jones) and Luke Cage
Drove Lola as Agent Coulson
Transformed from Lou Ferrigno to Hulk (Lou Ferrigno)
Transformed into Stan Lee (Hulkbuster)
Played as Harley Keener and Tony Stark in any level other than level 9
Died and respawned while playing as Aldrich Killian
Played as Fandral, Hogun and Volstagg in one sitting
Played as any version of Falcon and as any version of Cap, while in Washington D.C.
Visited all Hub locations
Played as Vision - both playable characters
Stopped 10 random crimes in Manhattan during a single session
Created and play as a Custom Character equipped with Mjolnir
Created a Custom Character
Turned on all Red Brick Extras at the same time
Unlocked and viewed all 15 Minikit Comic Pages
Completed 'Lost in the Aether'
Completed 'Ready A.I.M. Fire'
Completed 'Lack of Insight'
Teamed up Nick Fury and Quicksilver
Died and respawned while playing as Coulson
Completed 'Ultron Undone'
Completed 'Rise of Ultron'
Completed 'Korea Prospects'
Completed 'Anger Management'
Completed 'No Strings On Me'
Completed 'Earth's Mightiest'
Completed 'Avengers Assemble'
Transformed from Banner to Hulk
Completed 'Helicarrier Havoc'
Completed 'Shakespeare in the Park'
Completed 'Rail Hydra'
Completed 'A Loki Entrance'
Completed 'Struck Off the List'
Achieved True Avenger in any level
Set both Free Play characters as the Enchantress and Executioner in the Asgard hub area
Completed the 'The Masters of Evil' level with all Minikits unlocked
Defeated 20 enemies as the Black Knight (Dane Whitman) during Free Play
Completed the 'The Masters of Evil' level
Completed the 'The Masters of Evil' level after achieving True Avenger status
Completed the 'Classic Captain Marvel' level with all Minikits unlocked
Completed the 'Classic Captain Marvel' level
Completed the 'Classic Captain Marvel' level after achieving True Avenger status
Set both Free Play characters as Tic and Hawkeye (Classic)
Flew the Captain Marvel Skycycle as Captain Marvel in the Manhattan hub
Completed any race in the HUB using the Black Panther Skycycle
Completed the 'Classic Black Panther' level with all Minikits unlocked
Defeated 20 enemies as Killmonger in the 'Classic Black Panther' level during Free Play
Completed the 'Classic Black Panther' level
Completed the 'Classic Black Panther' level after achieving True Avenger status
Found a way to freeze Doctor Voodoo during Free Play in any area of the game
Set both Free Play characters as Baron Mordo and Dormammu
Completed the 'All-New All-Different Doctor Strange' level with all Minikits unlocked
Completed the 'All-New All-Different Doctor Strange' level
Completed the 'All-New All-Different Doctor Strange' level after achieving True Avenger status
Flew ''The Bus'' vehicle as Agent Melinda May
Set both Free Play characters as Agent Leo Fitz and Agent Jemma Simmons
Completed the 'MARVEL's Agents of S.H.I.E.L.D.' level with all Minikits unlocked
Completed the 'MARVEL's Agents of S.H.I.E.L.D.' level
Completed the 'MARVEL's Agents of S.H.I.E.L.D.' level after achieving True Avenger status