The best TV show for learning a language is one you’d like to watch anyway. This will help keep you from giving up out of sheer boredom early on. It’s also a good idea to find something set in the modern day, so you’re not learning outdated phrases.
Obviously, this all comes down to personal preference, but we’ve seen lots of people recommending Narcos, Club de Cuervos, and Ingobernable, which are all available on Netflix. If all else fails, just throw on your favorite show and switch over to Spanish audio to mix things up.