Six feet under. The last episodes with Nate, where he goes full asshole. And every episode that tried to push gay bullshit. Which were half of them, I think. How the fuck I even managed to watch so much of this shit?
House. Well, the ending was pretty bad, but at least it was over. In the same season there was a usual "supernatural" episode but this time instead of proving there was nothing special and curing the ill, they save them, but their family goes all "OOH IT WAS OUR MAMBO JAMBO THAT SAVED THEM". I think, this is where I realized that writers had given up.
Dexter. People say that the end of the original run was bad, but I'd argue that it was actually the finale of the penultimate season. Deb acted completely out of character, it sucked ass and no wonder that trying to build up on that lead to even shittier season and conclusion. Fuck, they were so desperate that they brought back that psycho chick Dexter was in love with in the most retarded way possible, she just happened to be there while fucking some rich guy on his yacht and she had no problem moving through Miami despite being a wanted criminal.
Better Call Saul. I think people give too much shit to the finale, because they mistake Jimmy fooling the court to save the last person who cared for him for a genuine remorse. He looks happy in jail because ironically he can be free there, he can be Saul Goodman and be respected by others. In any case, I didn't like the series much to begin with and the worst episode is either one where OMG LALO IS GONNA SHOOT GUS AND HE WILL NEVER APPEAR IN BREAKING BAD or the one where Lalo shot Hamlin, because it was really stupid, he just happened to be there, how is that their fault?
Sopranos. I'd say the finale and not for DON't... thing. I mean, what happens? Basically out of nowhere that FBI guy decides to give Tony "get out of jail free" card. The rest was ok.
Twin Peaks. I double that filler part in the second season. It contributed to nothing and sucked ass.