what have been the highs and the lows of the TV shows you have been watched?

As the thread title suggests, I’m curious to know what you consider to have been high points or low points in TV shows you have seen. It can be a show you enjoy very much or just something that you have happened to see, as long as you are able to differentiate ups and downs in a critical way.

A high/low point can be a very specific moment or it can be a stretch of episodes or even a whole season. However, it should be related to the overall quality of the show, in terms of acting, direction, production, plot lines, etc.