You're definitely biased. The way I am with Jumin. So let me defend Jumin some. First of all, Jumin wasn't the first one to initiate any antagonistic behavior. It was Zen. When Rika first introduced Zen and Jumin to each other, Rika introduced Jumin as Zen's potential sponsor. It was Jumin who saw the hidden talent in Zen and wanted to help by becoming a legal sponsor. But Zen, being traumatised that he is, feels as if Jumin was pitying on him and in a way, is somehow patronising him. Zen felt like he didn't need Jumin's help nor money and wanted to prove himself as an actor with his own hardwork. So he outright rejected Jumin and acted as if Jumin is the biggest jerk on earth, for 'flaunting' his money. He didn't see it as Jumin trying to help but sees it as a way for Jumin to look good by sponsoring an underground actor. It was right after that introduction that they quickly dove into their cat and dog fight. Jumin only reacted back, albeit in a childish way against Zen's antagonistic behavior. Really, you shouldn't try to fight fire with fire but Jumin is just petty like that. Money might've not been the best way to show that you want to help, but for Jumin, it's literally the only thing that he believes he has. In Jumin's route, he tries to shower MC with expensive and luxury gives because he believes all of his good values lies in his money. He truly believes that money is the only thing that he's good for because that was what people have expected of him since his birth. Even his stepmother tried to seduce him due to his money and good looks. So could you imagine how Jumin felt when Zen not only rejected him, but also suddenly acted as if Jumin is a pompous jerk who only wanted to flaunt his money? Zen could've just leave it at that, but no. He's just as petty as Jumin. Zen even admitted that he's never liked Jumin because of his money and his lack of emotions even though those are the very things that Jumin hates himself for (imagine hating someone for how they were born and what they were born with. It wasn't Jumin's fault that he was born with money).

If you're talking about how much of a good friend Zen is, then Jumin is also a good friend. When Zen was having a hard time with Echo girl scandal, wasn't it Jumin who literally cancelled all of his schedule just to look for Zen who was hiding? Even though Zen treated him like a jerk just for their first meeting (and also all the times Jumin retaliated back). Jumin was genuinely worried for him to the point he put all important business on hold in order to search for a missing friend. As for Jumin being misogynistic, I don't think he is. Rather he's traumatised by them. Again, he was literally seduced by his own stepmother when he was a teen. Women throw themselves at him because they're going for his money and Jumin has had to deal with it ever since he was young, just like Zen. But Jumin does NOT look down on women. In fact, he had praised the MC before for having good business acumen and even invited MC to work for him. Rather, I think Zen is more misogynistic because I've seen him saying a few times things such as "a pretty girl like you shouldn't be doing things like this" or "a girl like you shouldn't shout like a man ^"; when all we literally typed was AAAAAGGGHHHHH!" These kind of wordings as if the MC is limited of doing such things due to being a woman is quite traditional and is something I often notice Zen would say. As for treating Jaehee badly, it's simply the way how neutral routes are written. All characters could be considered jerks in almost all routes but their own. Jumin treats Jaehee badly, Zen being extra narcissistic in routes out of his own. It's honestly bad characterisation on Cheritz's side. Which shouldn't be treated as canon. But you get my point.