Season 2
The first half of the second season deals with the team facing Thanos, as he competes with them to obtain the Infinity Stones, followed by a five-episode arc detailing the return of Ultron, who plans to exterminate the human race. The rest of the season details the arrival of the Squadron Supreme and their confrontation with the Avengers.
Episodes
1. The Arsenal
When Red Skull comes crashing to Earth with a fleet of alien ships chasing him, the Avengers learn there's a villain in their midst a thousand times more dangerous than the Cabal ever was: Thanos! Earth's Mightiest Heroes are forced to face the fact they're big fish in a small pond -- and this new villain wants to conquer the entire ocean! Will the mightiest superheroes on Earth be able to stop the super-villain of the galaxy... before he succeeds in becoming all-powerful?
2. Thanos Rising
With the help of Arsenal, a robot created by Howard Stark for Tony, the Avengers must stop Thanos from gaining the Power Stone - an energy force so powerful that it could cause mass destruction.
3. Valhalla Can Wait
Hulk and Thor are tricked into a battle and transported to Valhalla to find out who is the strongest, once and for all. But under Hela's rule, only the loser of their contest may return to Earth while the winner will become her consort and champion.
4. Ghosts of the Past
Red Skull has information that could help the Avengers save the world from Thanos, but an intruder kidnaps Skull before they can retrieve it. Cap discovers that the trespasser is none other than his old partner Bucky Barnes, now the Winter Soldier, who's back and seeks revenge.
5. Beneath the Surface
When Hawkeye and Black Widow stumble upon the Serpent Crown, they must work together to stop Attuma's battalion from destroying Atlantis.
6. Nighthawk
When a mysterious new villain uses the individualized counter measures Falcon created when he was at S.H.I.E.L.D. to take out the Avengers one by one, he must figure out a way to save his team.
7. The Age of Tony Stark
When the Time Stone becomes attached to Tony's arc reactor, it causes him to de-age and brings dangers from other eras, including dinosaurs, into present-day New York City.
8. Head to Head
Tony believes the Avengers have reached the pinnacle of perfection, but when M.O.D.O.K. uses the Mind Stone to assume control of S.H.I.E.L.D., the team is put to the test as they are forced to swap minds.
9. The Dark Avengers
In a 'flipped reality,' the Avengers discover that their world has been reshaped by the Reality Stone, wielded by the Squadron Supreme. In this new reality the Squadron Supreme have made themselves the heroes and the Avengers the villains! Find out if the Avengers can take down the Squadron Supreme and prove that they're the real heroes.
10. Back to the Learning Hall
When Thor is tricked into returning to Asgard, he and the Avengers discover they must defeat Loki and prevent Earth and Asgard from crashing into one another and foil Loki's plan to escape Valhalla and seek revenge on his brother.
11. Downgraded
Stranded without his gear in a dangerous realm where technology doesn't work, Falcon must prove to himself and a skeptical Hawkeye that he's still a hero.
12. Widow's Run
The Avengers must protect Widow and Thor as they carry out Widow's plan to rid the Earth of the Infinity Stones before Thanos arrives to claim them and control the Universe.
13. Thanos Triumphant
With the power and might of all five Infinity Stones finally in his gauntlet, Thanos plans to wield his power over the Universe while the Avengers make a desperate attempt to stop him.
14. Crack in the System
Iron Man and Captain America try to rebuild their relationship, until Cap discovers Iron Man's hiding dangerous information about an artificial intelligence unit named Ultron.
15. Avengers Disassembled
An even more powerful Ultron resurfaces and takes control of Avengers Tower and Iron Man's Hall of Armors, leading to the destruction of the Avengers as we know them.
16. Small Time Heroes
With the team divided and the Avengers Tower wiped out, Tony seeks help from Ant-Man. Learning he's busy fighting MODOK, Tony's team joins Ant-Man to stop the Pym Particle thief.
17. Secret Avengers
Working for S.H.I.E.L.D. isn't everything Captain America's team had hoped when they're expected to unquestionably follow orders involving the Crimson Dynamo and The Winter Guard.
18. The Ultron Outbreak
The Avengers reunite when Captain America and Iron Man learn to appreciate their differences while trying to save the world from ultimate destruction at the hands of Ultron!
19. The New Guy
When Ant-Man joins the Avengers, Hawkeye resigns and trains his replacement on Monster Island, unaware that Red Skull is nearby planning to cloak himself using Dormammu's powers!
20. Terminal Velocity
The Squadron Supreme's fastest member Speed Demon is on the loose and wreaking havoc throughout Avengers Tower. Hulk must save the day by fighting the high velocity villain. Meanwhile, the other Avengers face off against Hyperion.
21. Spectrums
New Avenger, Ant-Man, begins to atone by bringing his former allies to justice. His quest for redemption leads the team to an epic battle with Squadron Supreme's Dr. Spectrum.
22. Midgard Crisis
Thor is convinced that Zarda wants to defect from Squadron Supreme, but Hulk knows better and must protect Thor from Zarda's duplicitous ways.
23. Avengers' Last Stand
Falcon tries to prove he can be a leader when the Squadron Supreme enacts their end game and kidnaps Captain America and Tony. Things become even more difficult when the Avengers discover the Squadron Supreme's last few plots were all part of an even bigger plan to revive their previously unknown sixth member named Nuke.
24. Avengers Underground
Unbeknownst to the Squadron and the rest of the world, the Avengers are in hiding and working on a plan to save the planet and stop the Squadron Supreme once and for all!
25. New Frontiers
When an alien race begs the Avengers to save them from mysterious invaders, the team discovers that a recently-escaped Thanos and his Black Order are plundering the planet. Meanwhile, Tony seeks new challenges for the team.
26. Avengers World
When Thanos attacks Earth, planning to finally take over the planet by destroying the Avengers, the team discovers they are more than eight heroes - they are an ideal.