It is dramatic, it has action. Humor is one of the least noticeable qualities of the fight. It's funny, you mention people talking about Saitama Vs. Garou in the WC being serious a lot, you wanna know why? Because 90% of people agree it is, and not because of some refutable or subtle reason. The tone of the entire fight from beginning to end is serious, even if it has humorous elements. You're portraying it as a big joke of a fight when it's really not.
These things don't make it comedic. Cathartic is hardly the right word to use here btw despite how much you are using it. Also it's really not as one-sided ideologically as you're saying. Saitama tells Garou that he's basically doing something stupid and that it'll never work because Garou can't beat him, Garou doesn't have some "I'm enlightened, you were so right!" moment where he abandons what he believed suddenly because Saitama hit him a few times. Garou gives up and leaves.
Relevance? It doesn't undermine his character.
A Hero cosplaying a Monster you mean. And again, relevance? The narrative constructs Garou as someone who wants to do good things and protect the weak who cannot protect themselves, but he does so by alienating himself, villainizing Heroes, and wanting to stand against the self-proclaimed justice of the world that ignores people who need justice the most. That's not a joke nor comedic. It's nuanced character writing.
The stake is what's going to happen to Garou, a character who's taken half the spotlight for an entire arc that most of the readers have come to like. It's more than Garou getting humbled, it's everything he's worked towards over the entirety of this arc crumbling to dust because he encountered an anomaly that supersedes any level of growth he could hope to naturally muster through his will power and talent alone. He views Saitama as the embodiment of the unfair justice of the world that caused him to adopt this mentality in the first place.
It has similar narrative elements but it is very different. Garou wasn't being portrayed as a LITERAL deluded manchild unlike the members of Claw, speaking of, that fight and scene weren't gags either, they had comedic themes, very much so, but were still moments of actual writing and narrative complexity as well as character growth, to refer to it as a joke would be to insult the writing, nor were Garou's efforts so easily swiped away like Claw's were, which is ironic because the power gap between him and Saitama is bigger than 1000% Reigan Vs. the Claw members, Saitama was allowing him to actually give it his best and Garou put in real effort into it, it was only a little over halfway through that Saitama decided enough was enough and put the beatdown on him. If that's what you think the fight amounted to, I'm seriously questioning your ability to comprehend narrative.
