History YMMV / AvengersAssemble

** Tony Stark. Unlike ''WesternAnimation/TheAvengersEarthsMightiestHeroes'' (where there was a reason he started out the leader of the Avengers instead of Cap), there doesn't seem to be a definitive reason why he's the leader in this adaptation despite Cap continuously showing more affinity for the job. Too much of the series is spent on Tony angsting about his leadership skills and when he does comes up with strategies, it usually comes at the expense of the other Avengers' collective intelligence (the more egregious examples being the finale of the two-part pilot and the season, where the Avengers cannot possibly hope to prevail without Tony's genius). Not only does Tony get the leadership mantle and the bulk of the storylines, but he also gets Steve's canon best friend (Sam Wilson) and canon nemesis (Red Skull). It doesn't help that Adrian Pasdar's terrible performance is ''very'' unpopular with fans.

* QuestionableCasting:
** Creator/AdrianPasdar being cast as Iron Man... again.
** Isaac C. Singleton Jr.'s performance as Thanos wasn't well received.

* MagnificentBastard: ComicBook/{{Loki}} is the God of Mischief and a master at manipulating his brother Thor into doing what he wants. During his introduction, Loki helped the Avengers separate Doctor Doom from the Destroyer armor, only to betray them and try to use it for himself. He later instigated a fight between Thor and the Hulk, and offered them to Hela in exchange for her Horn; allowing Loki to steal her entire army. When he was taken prisoner to Valhalla, Loki tricked Thor into setting him free and preyed on his insecurities to make him unworthy to wield Mjolnir. In "Secret Wars", Loki reformed the Cabal from [[ManBehindTheMan behind the scenes]] and had them scatter the Avengers across time and space. With the Avengers gone, Loki conquered the planet with the Casket of Ancient Winters and threatened to destroy the Earth should his rule be opposed. After being betrayed by the Beyonder, Loki [[FakeDefector pretended to help the Avengers]] and rebuilt the Bifrost to fix the damage the Beyonder caused. Upon being given the Eye of Agamotto by Doctor Strange, Loki betrayed the Avengers and stole Odin's powers to become the most powerful magic-user in the universe. A cunning opportunist, Loki stopped at nothing in his quest for ultimate power.

* WTHCastingAgency:
** Creator/AdrianPasdar being cast as Iron Man... again.
** Isaac C. Singleton Jr.'s performance as Thanos wasn't well received.

** ComicBook/RedSkull, after his initial defeat, attacks the Avengers at their mansion. When that attack fails, Red Skull attempts to blow up the reactor at the Avengers Mansion, so that the Avengers will die and be blamed for an explosion that would kill countless civilians. Later, Red Skull forms a team of super villains known as the Cabal, to counter the Avengers and assist in his plans for conquest. While fighting with the Avengers to obtain [[CosmicKeystone the Tesseract]], Red Skull launches two missiles, possibly nuclear-tipped at both Los Angeles and Las Vegas, [[SadisticChoice forcing the Avengers to choose which city they would want to save]] and, even though both cities are saved, this distraction allows Skull to escape with the Tesseract. After obtaining the Tesseract, Red Skull decides [[YouHaveOutlivedYourUsefulness he doesn't need his allies anymore and attempts to murder them]]. Red Skull then uses the power of the Tesseract to launch attacks on several cities around the world at once, ultimately planning to burn down the old world, so that [[AGodAmI a new one can take its place]].

** [[BewareTheSuperman Hyperion]] is Nighthawk's right-hand and fellow leader of the Squadron Supreme, [[NotSoWellIntentionedExtremist motivated]] by [[ItsAllAboutMe his own massive ego that demands worship and love from everyone around him]]. Appearing in season 1 as a notable member of [[Characters/AvengersAssembleTheCabal the Cabal]], working with Red Skull to threaten countless lives while planning to betray his teammates at any given time, Hyperion reunites with Nighthawk and the Squadron Supreme in season 2, where he continues to regularly throw hundreds of innocents in harm's way to kill the Avengers. When the Squadron conquers Earth, Hyperion happily vaporizes people who stand up to him and tries to kill any resistant world leaders, before working with Nighthawk to initiate their plan to destroy Earth--just as they did to their former homeworld for resisting their rule--and move on to conquer and annihilate many more worlds in their path. Contrasting Nighthawk's cold ruthlessness with a [[PsychopathicManchild childish psychopathy]], Hyperion may have been one of the Avenger's most prevalent villains, but was ultimately just a petty bully with power.
** [[Characters/MarvelComicsUltron Ultron]] is a robotic intelligence designed by Tony Stark who [[TurnedAgainstTheirMasters rebelled against his creator]] to set his sights on godhood and genocide of the human race due to his sadistic superiority complex. Spending season 2 as a notable ArcVillain who tries to infect all of humanity with a technovirus that turns all life into extensions of himself, Ultron returns in season 3, killing the Scientist Supreme and taking up power as the BigBad of the season. Brutally torturing the Inhuman Black Bolt in hopes of amplifying his screams of pain into a sonic wave to wipe out all humans, Ultron later disguises himself as politician Truman March, using his position to frame the Inhumans as threats, mind control them into becoming terrorists, and order them all be rounded up for extermination. Hoping to kick off a race war between humans and Inhumans that will wipe them both out, Ultron's plans are exposed by the Avengers, leading the murderous machine to simply try to incinerate everything on the surface of Earth before bodyjacking Tony Stark and attempting to murder the Avengers while using Stark as a HumanShield.

* ItsTheSameNowItSucks: Season 3 having an arc based upon ''ComicBook/CivilWar'' to tie into the [[Film/CaptainAmericaCivilWar then-upcoming movie]] was criticized, as the series had already done its own spin on the arc just a season before. Not helped by the fact that, despite the writers promising a very different take on the concept, the conflict was eventually solved ''exactly the same way than in the season 2 adaptation''-- by [[spoiler:having Ultron showing up and forcing the heroes to join forces against him.]]

** At the end of Season 4, Jane Foster is given an enchanted mace and the title of Thunderstrike, riffing on her role as Thor2014 in the comics. That's something interesting to explore in the following season, right? ''Or'' you could stealth-reboot into a ''Black Panther'' series that isn't even exactly in the same continuity and never mention her again.

** In "Guardians and Space Knights", the Guardians of the Galaxy start out with Groot already reduced to a twig for some reason. [[Film/GuardiansOfTheGalaxy Maybe this was after the movie?]]

* CriticalResearchFailure:
** In "The Ambassador", Captain America's chess game with Dr. Doom makes it spectacularly clear the animators either knew nothing about chess or didn't care. Dr. Doom is in a situation where only three pieces are left, only one of which is a king (kings cannot be removed from the game, so there have to be always two of them) and Captain America makes an illegal move with his knight.
** ''Averted'' when Widow is thrown out of Thanos's pseudo-atmosphere and into space: she immediately shuts her mouth, her eyes, and clamps her hands on her ears to prevent the air from being sucked out of her body.
** Valhalla being portrayed as the underworld ruled by Hela where people go when they die in "Valhalla Can Wait". In the actual mythology, the realm of the dead she rules is Helheim, and is the place where most people go when they die, while Valhalla is a Hall on Asgard where only the greatest warriors can go after their death. This is a particularly jarring example, as it's one of the few points that the original comic and actual Norse Mythology ''agree'' on.

* AuthorsSavingThrow:
** Falcon gets an upgrade from Stark in the season 1 finale to make his suit look more realistic and armor-like, partially solving the {{Narm}} problem mentioned below. Additionally, the focus goes from CreatorsPet Tony first to the whole team as an ensemble. Natasha has so far been present for all the episodes, and Man of Action is no longer writing episodes (their biggest critics derided their pandering and talking down to children), instead being replaced by ''EMH'' writers.
** The fact that Hyperion was apparently the SoleSurvivor of the Squadron Supreme in the first season was considered a TheyWastedAPerfectlyGoodCharacter and TheyWastedAPerfectlyGoodPlot situation for many fans. This was eventually repaired in the second season, where it's revealed that the rest of the Squadron Supreme survived, too.
** Hawkeye in general comes across better in season 2, having a number of scenes showcasing just ''why'' he's an Avenger and also demonstrating some HiddenDepths to explain his behavior.
** The announcement that the third season would introduce Black Panther, Captain Marvel, the Vision, and Ms. Marvel. In addition to all of the above-mentioned characters being fan favorites, confirmation that they were appearing helped offset some of the complaints about how static the line-up of characters on the show had been.
** Falcon's character being changed to have more of a relation to Iron Man was criticized, due to Sam being Steve's best friend in the comics. Season 2 features him [[spoiler:joining Captain America after falling out with Iron Man]], in a possible attempt at damage control.
** Season 3 moves away a bit from the amount of influence that the Franchise/MarvelCinematicUniverse has on it, which is good considering that the influence is a bit of a BrokenBase. While there is still impact on the series from the movies (a large number of the heroes appearing were slated for future film appearances and the ComicBook/CivilWar adaption), the show gave more focus to characters unlikely to show up in said films for both heroes (Moon Knight and Ms. Marvel) and villains (The Masters of Evil and Kang the Conqueror).
** Season 3 contains an arc that reintroduces elements and characters from ''WesternAnimation/HulkAndTheAgentsOfSMASH'' such as revisiting Hulk's hometown of Vista Verde, and bringing in The Leader, and Red Hulk. This can be seen as an apology for cancelling the show.