The Episode Where Cotton Dies
That episode was one of the stupidest, most poorly written, least funny, unbelievable and cringe worthy episodes of the series. You can tell by this point the writers were wanting to end the show but FOX kept renewing it and they weren't trying it anymore.
Not only was it unrealistic, it portrayed Cotton as being completely evil when in earlier episodes he was shown to be sexist and hateful but deep down inside he cared about others even if he cared about himself first.
I hate that episode. In fact I hate just about every episode of King of the Hill after Lucky came along. That is when the show Jumped The Shark.