Luke Cage for Brian Michael Bendis, whose run on the book saw him go from Hero For Hire to leader of the New Avengers, and is one of three characters (the others beingWolverine and Spider-Man) to remain on the team for the entirety of the first two volumes. While he did become a more mainstream character under Bendis, many grew tired of his exposure over the years.
Similarly, Jessica Jones, who was merely a supporting character in the first volume before becoming a full fledged member of the team following Dark Reign and actually was created by Bendis. While she was initially a very liked character, especially due to Alias, fans grew tired of her very quickly, due to her seemingly needing to be in everything.
Franchise Original Sin: Much of the criticism of Bendis' writing actually has always been part of his work, it's just that it's more noticeable when he's writing a plot-driven superhero book with a large cast as opposed to character-driven street-level stuff focused on a handful of characters.
His repetitive, casual dialogue that has characters sounding the same. With less characters, many of whom are street-based, the casual tone makes sense and humanises his characters. When he has tons of characters with vastly different personalities, characters all talking like the same smartass stands out a lot more.
His Writing by the Seat of Your Pants-style of writing works in character-driven work because the stories were focused on character development and interaction. New Avengers tries to make its plot feel important and character work is an afterthought, as most of the characters had their own series where their character work was more important.
Hilarious in Hindsight: In an early issue of the series, Daisy Johnson is needed and afterwards, she declares that her Avengers codename will be Quake. Steve then informs her that they aren't looking for new recruits. Years later, during Hickman's Avengers, Tony and Steve are expanding the lineup, and right there on a list of recruits is Daisy Johnson.
Ho Yay: When the embarrassing truth came out that Jessica Jones had a crush on Peter Parker when they were in high school came out, Spider-Man attempted to reassure Luke Cage that he had no designs on his wife. He then went on to ask if the way were clear to Iron Fist...
Narm: Ms. Marvel's idea of an insult? Calling someone a "hump".
The Scrappy: The Sentry is universally hated by this point.
They Changed It, Now It Sucks!: The reaction a number of "old school" Avengers fans had, with the initial line-up featuring only two classic Avengers and the shift away from the global level threats the classic book dealt with.
They Wasted a Perfectly Good Plot: In the opening story of vol 2, it's stated that the Vishanti, the Big Good as far as magic is concerned in Marvel, are no more. Despite the fact that this should be a world-shaking event, it's never brought up again.