I think everyone heard that at some point - "Meh, that just a C-grade supervillain dude, nothing to worry about", of "What are you C-listers thinking trying to fight Ultron?"
Little doubt that Captain America and Avengers are A-list superheroes, hell, "A" might as well stand for an "Avenger" here. However when I was asked to define B- and C-league heroes\villains, I got a bit stumped. The best I could come up with is "B-grade are guys, who are not Avengers", and "C-grade are dudes, who're not only not Avengers, but have no respect because of that."
However this division is evidently flawed - take Moon Knight for example. Dude is hardly ever can be solidly put in A-list, yet Cap trusts him to be an Avenger. Or Livewires. So I've got a question - are there a way, or a list, of classifying characters to this grades, without resorting to obvious popularity ratings?