I wish I'd stopped watching The Walking Dead partway through season 5, whenever Rick and friends arrive at Alexandria, but before they go inside.
Sure, there's plenty of good episodes/moments afterward, but without spoiling anything, that's also when a lot of the show's bullshit really ramps up.
Jericho only lasted 29 episodes, and while I enjoyed them all (plus the graphic novels that continued the story), I will admit it had a shaky start.
It was a mid-2000s CBS show, so it had to appeal to a wide audience, the kind who'd tune in to CBS of all networks during primetime. The show's overall premise had me hooked, but some of the side plots and characters are... distracting, early on.
Most people agree that the show picks up steam partway through the first season, though I haven't seen a consensus about a particular episode. My pick though, episode 7, "Long Live the Mayor".