/jp/ - Otaku Culture

What would be the best way to write a human wizard that can go magically toe-to-toe with a Baphomet General without him coming off as mary-sueish? Would it just be to establish limits to what he can do or something along those lines? It's not like he'll be some super-famous bigshot known the world over, he'll have a background of mostly keeping to himself whilst seeking to learn and research anything that interests/fascinates him.

How does this even work?