Uh, No the fukk she isn't. Secondly If she comes out of literally nowhere to save The Avengers then yes she is a Mary Sue. She has no connection to the Avengers other than Marvel wanted to make a female superhero movie, I'm fine with that. Marvel is pandering, I'm fine with that too. But don't act like Captain Marvel has some HUGE fandom either.She isn't anywhere near Wonder Woman or hell even Harley Quinn realistically. Yeah them white boys are pissed for a doofy ass reason. But as someone who has stuck with the MCU since its inception, i can see why SOME fans would be legit angry.