Two very common views people will adopt to demonstrate the above:

The gender pay gap: clearly there is no legitimate or natural way that men would make more money than women in a fair system, so the system must be biased against women.

The gender academic success gap: boys don't pay attention or do their work so it's only natural for girls to do better.

It's clear that for both of these thoughts to exist in someone's head, they must think there's a superior gender.