Garren Jacobsen
Auror
I understand from a realistic perspective that someone like Ronda Rousey would have very little chance against someone like Cain Velasquez, but I write pure fantasy and in my worlds, it wouldn't be surprising for one of the heroines to call Gregor the Mountain 'The Molehill' and then kick his ass in a toe to toe battle. Just a matter of style IMO.
Fictional men surpass the limits of what should be a realistic male character all the time after all, why shouldn't fictional women XD
True, but there needs to be a good reason for it, even if it's a bit of hand-waveium. Saying she is quick, smarter, etc. is a good reason. It might not be realistic but it'll work well enough. But if you say that an Arya character beat a Clegane character without a mentioned justification not a single person would believe. They, like I, would toss the book and call BS.
To your fictional men point there is always a reason why they're defying basic facts of life. When applied logically it may not actually work, but it's still a reason and readers will say, "I can accept that." The same must apply to women as well.