It's like a cis person, but they identify with their gender even more than 100%. A supergender male, for example, might feel that he is 500% male and inject himself with a bunch of shit that'll probably not be very good for him, just to reach a supreme degree of masculinity that no standard cis man could ever reach! Supergender people are valid too! Some synonyms for the term include: gigagender, ultragender, hypergender, and megagender.
hmmm what about the opposite, when someone transitions to the opposite gender but also identifies with it 500%? Would that be supertransgender? Or subgender?
You gave me the best idea for this one. We'll call them "domgender" because they're dominating cisnormativity by not just transitioning to the opposite gender but doing so in a way that makes them SUPER like the opposite of their birth gender, effectively making transphobia their cuffed-up bitch.