I would also recommend the Armorer's Handbook supplement from dmsguild. It gives martials more options. Having upgraded armor really makes it easier …

How about a non anime example then? A level 20 barbarian should be strong as Heracles

I'm sorry, but a level 20 fighter should be moving like stark from frieren. Not just swinging a sword four times.

Dragons by miles, given that if they become old enough, they become dragon ascendents, which is treated as a form of quasi deity.And of course, bonus…

you are the goat

Are you still waiting?