Aside from Marvel's discomfort with women with too much power (see also:Jean Grey),
Sometimes just a character, male or female, has too much power and that can be Marvel's discomfort. A good example is Sersi, who can turn anything into anything else: if she can turn all the bad guys into pigs, we have a very short story. The Silver Surfer can tap into the Power Cosmic, so he usually fights cosmic level foes in outer space and rarely teams up with the Avengers.