Just to ask but, who's the fish that you believe is underhated and vise versa (overhated)?
I think a lot of hate comes from production fucking up and giving bad direction to the fish.
Brian's a weird character. He was hated in season 2, because he was told to make the audience hate him, and then people liked him in Bloodgames when he wasn't supposed to be hated. So he actually did a really good job, it's just that the job he was given was actively stupid. I assume they wanted a "heel" character, but he did it by acting like a slimy Jew and wasn't actually entertaining. I think it was just really bad direction from Jet.
Mizzy was overhated, they were both playing the game that production had set up. Mizzy was hated early on for yapping, which admittedly wasn't entertaining, but the only direction she had at that point was to scheme for the voting. She got the most hate over the "threats" to production, but I still think those were misunderstandings / poor direction: She was let in on a secret that could ruin the show and was given no direction beyond keeping it a secret. Production told her that she didn't need to help convince anyone, but her only choices were to either spill the beans or help cover them up and she couldn't spill the beans. The actual threat was "did you want me to tell everyone?" after she thought she was being punished for finding out somehow. Production interpreted that as a threat, but I really think it was asking for direction. She constantly played the role she was given, which is what she was hired to do. Once she figured out the point of the show was to be hostile, she got kicked for being hostile.
Binx was overhated for basically the same reason. She did everything she was told to do and got hate for it. Even knowing about Fishtank: The first two seasons had plenty of people pretending not to know, and they're the ones who told her it was fishtank to begin with. The troon thing was part of the game, which he won by kicking Simbal, and I stand by that she was correct in not giving a shit about the guy: it didn't make sense to make herself a target or throw away her vote to do productions' work for them, and being upset about being yelled at by Sam for following production's instructions is justified.
Jon was overhated in Season 1 after his return, he was just acting the way that fans told him to act.
A lot of people have said Jimmy is underhated, but I disagree: he was on a show where people are supposed to get mad and throw shit, and he got mad and threw shit. The impact wasn't on camera: clearly he didn't hit her directly or she wouldn't have been okay, presumably it hit her on rebound. Was he trying to hit her and missed, or was he trying to miss her and hit? If you take him at his word (and maybe you shouldn't) it's the latter. The mallet throw isn't even the worst injury in season 2, TJ got his rib broken due to retarded boxing stuff, and Shinji probably could have killed TJ if he'd went for blood during the boxing match at the end (and it seemed like that's how production wanted him to fight). For the record, I'm not saying Jimmy shouldn't get hate, I just don't think he deserves more than he gets.
TJ is both over and underhated: His plot/arc was dumb but it wasn't his fault, but the weird gooner shit was absolutely real. Lie detectors aren't real.
Mostly, though, Sam is underhated. Most hate towards production gets directed at Jet, but a substantial number of the problems are Sam's fault. I maintain that the biggest fuckup in season 1 was the handling of the baby stuff and Simmons. I still think Simmons wasn't actually a pedo, just ESL, and we missed out on the Jon - Simmons relationship due to it and probably lost Jon over it. Letty and Vance got punished for the baby torture, which made them less aggressive than they could have been. Supposedly the RV trip was his idea. The boxing stuff was his idea. Etc.