Rogue and the Scarlet Witch calling out Magneto for being a cold hearted killer when he crushes the Red Skull's head. Did he really deserve it or is it very poor writing considering that the Red Skull is one of the most despicable people in the entire Marvel Universe who supported the concentration camps Magneto was forced into?
Issue #7 retconning Magneto's relationship with Quicksilver and Scarlet Witch, revealing that he's not their biological father. The reaction to this ranges from relief that the Maximoff twins can now have stories and character development of their own without having to rely on Magneto and the X-Men to sheer outrage at throwing out several decades worth of development between the three. The subsequent retcon that the twins were never mutants, however, is universally agreed to have been a bad one. It doesn't help that this was motivated entirely by real life, out-of-universe issues surrounding the movie rights of these characters rather than any actual story reason either.
Crosses the Line Twice: One scene involves the inverted Carnage praying for forgiveness by saying "I admit I want to murder everyone all the time but I'm trying super-hard not to right now". His "heroic" actions are also comically horrible. For example, he stops a bank robbery by burning down the bank before the robbers get there.
Inverted Carnage, whose awful attempts at being a hero are hilarious to look at. Even people that didn't like regular Carnage are fans of him.
Also the inverted Doctor Doom because he has his own team of Avengers. He also got some respects for reviving Cassie Lang.
Inverted Hobgoblin for his self-promoting tactics and being completely tongue in cheek with all his heroic exploits including (but especially with) constantly making a fool of Phil Urich.
Stingray has gotten a lot more cred than he used to thanks to his unexpected badassery in the Avengers World tie-in.
Fanon Discontinuity: As far as some fans are concerned, Quicksilver and Scarlet Witch were not retconned as actually not being the children of Magneto. Marvel seems to be slowly reversing this since Marvel Ultimate Alliance 3: The Black Order has Scarlet Witch explicitly be identified as a mutant (another retcon shortly after the event remove her and Quicksilver's status as mutants) and subtle interactions with Magneto have implications that they are still a family.
Jerkass Woobie: This trait of Magneto is emphasized more than ever here. In the end he loses the Jerkass part by completing his Heel–Face Turn.
Bizarrely the inversion has made Carnage into this. He genuinely wants to help others now but has to constantly fight his old personality's violent impulses and spends some of his panel time praying to God for forgiveness.
Just Here for Godzilla: Many fans tuned in just to check out the awesome and hilarious depictions of the inverted villains like Deadpool, Carnage, Doctor Doom, and Hobgoblin.
The inverted Captain America crosses this when he betrays all of his teammates with Pym Particles he forcibly sapped from the Wasp, an action that horrified even inverted Havok.
The inverted Iron Man crosses this when he creates a Freemium Extremis app that creates a new breed of class warfare between those who can afford the app and those who can't, all while caring only about the profits. When Daredevil confronts him over this, Tony throws him out of his estate.
An inverted Hulk is a good enough idea, but there have been previous versions of the character. This could have easily set the stage for the return of the Devil Hulk or Guilt Hulk, and instead Kluh was invented for the role.
More broadly, a number of fans and reviewers have pointed out that most of the inverted heroes are acting in rather generically evil ways, though the characterizations of the inverted villains have been met with praise for the way the baddies are portrayed as retaining their negative traits even when trying to do good.
From the inverted villains side, Jack-O-Lantern was barely shown at all. The nature of his inversion was almost never explored in contrast to pretty much everyone else.
Unexpected Character: The Hobgoblin tie-in features a bunch of obscure characters such as D-Man and Wildstreak as Kingsley’s new proteges. Hell, the first issue even features a new Hindsight Lad of all things.
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