There are a lot of annoying and dislikeable characters in this story but for me Motoyasu is by far the worst of the bunch
I can only disagree. Even when he's being unlikeable, it's at least sometimes portrayed in a "cartoonish comic relief" kind of way, so there are plenty of times where you can just call him a bumbling buffoon and move on. Plus, he's currently not nearly as bad as he was at the beginning of the story, I think.
No such luck with
Malty Bitch, whose schemes and manipulative tendencies constantly bring out the worst in her victims—Motoyasu being one of them, even—by preying and capitalizing on their insecurities. There is truly not a single redeemable bone in that body of hers, and it is never, ever played for laughs; she is just a vile human being, through and through.