@mage_goo
Did you forget? He spent all that time single-mindedly focused on killing the MC and those he hated. He didn’t even immediately recognize the girl when he woke up.
His familiars may have done all the work, but did you also forget that he himself could fight? He personally fought them himself when his familiars couldn’t do the job, and they all almost lost. In other words, he was that strong to begin with.
Also, who are you to judge how determined a person can be? People have varying levels of determination that have no legit means of being measured.
How can the magic theory be fake? If it works, then how is it fake? Do you know the laws of causality that govern that world? It’s impressive that you’d claim to know more about the author’s own world than the author themselves.
You even forgot the most basic thing is that the guy’s level and power have nothing to do with how he looks. Muscle atrophy is a visible thing, but how can you be sure that magic isn’t coursing through his body to supplement that?
I get you wanna complain, but complain about things that actually make sense.