pyro

since the enemies are visibly set on fire, you can very easily use Pyro to spot invisible and disguised Spies.

Although it is classified as an attack class, it has some defense class qualities, some examples are its "Compression Blast" can reflect enemy projectiles and also extinguish its allies when they are burning.

Agreeing with "Meet the Pyro", Pyro imagines himself all over a happy world called "Pyroland", where his "Enemies" as babies

It is quite possible that Pyro suffers from Schizophrenia, a disease that distorts reality, due to his hallucinations that cause him to see everything through a childish utopia called Pyroland.
Although it could be due to his mask

Who is Pyro TF2? The Pyro is a human being with an obsession with pyromania, of undetermined origin who only whispers through a mask that hides a burning passion for all things related to fire.

Pyro was never known to be a woman or a man.