Spoilers for X-Men Annual #1 by Marvel Comics
On Krakoa, one X-Men hero is learning that being an Avenger has become an insult among some mutants, as Firestar is called out for previously fighting alongside the team. In X-Men Annual #1 by Marvel Comics, Firestar's former allegiance with the Avengers puts her in the bad books of some Hellions on the mutant paradise, who use the team name of the Earth's Mightiest Heroes as an insult against the newest member of the X-Men.
In X-Men Annual #1 by Steve Foxe, Andrea Di Vito, Sebastian Cheng, and VC's Clayton Cowles from Marvel Comics, Firestar is attacked by a group of Hellions on Krakoa. The group of mutants is mad that the hero has joined the X-Men when she's only recently aligned with mutants. When Roulette calls Firestar an "Avenger," the hero can't help but note that she says the world like it's a slur, as her time with the superteam is seen negatively by her attackers.
Firestar's Avenger Past Has Made Her A Easy Target By Her Fellow Mutants
Firestar joining the X-Men has been controversial among Marvel's mutants, as Angelica Jones previously tried to separate her mutant heritage from her life. Before joining the X-Men this year, Firestar had been a member of the Avengers, the Young Allies, and the New Warriors. So, when the hero, who has the powers of energy generation and manipulation, finally accepted Emma Frost's offer to join her fellow mutants on Krakoa, she wasn't exactly welcomed with open arms. In Firestar's most recent confrontation with the Hellions, her past as an Avenger is used as an insult, as her fellow mutants can't believe she was chosen to represent them on the X-Men.
While the mutants on Krakoa have a right to be upset with Firestar being chosen as a member of the X-Men, despite her past reluctance to be among her fellow mutants, putting her down by calling her an "Avenger" is a pretty weak insult. As Starfire points out, Wolverine, Beast, and current X-Man Havoc have all been Avengers in the past - so it's not like she's the only mutant to suit up with Earth's Mightiest Heroes.
Ultimately, Firestar is trying to make an important change in her life and fight alongside the X-Men while embracing her mutant heritage like never before. But, unfortunately, some other mutants, like the Hellions, aren't willing to look past her time with the Avengers and other superteams and are using the term "Avenger" as an insult to the X-Men hero - even if doing so is hypocritical, given other mutant's joining the team before.