16. Gilmore Girls, Season 7 (The CW; September 22, 2006 - May 15, 2007)
Series creator Amy Sherman-Palladino's mile-a-minute pop-culture-reference-laden cadences made her the undipisuted master of teen angst comedy dialogue with Gilmore Girls. As this list bears out, a showrunner leaving is damning to almost any series. Sherman-Palladino may be unique, however, in that she may have been the first showrunner to leave a show citing too much creative control.
She told Vulture, "It was a botched negotiation. It really was about the fact that I was working too much. I was going to be the crazy person who was locked in my house and never came out. I heard a lot of 'Amy doesn't need a writing staff because she and [her husband] Dan Palladino write everything!' I thought, That's a great mentality on your part, but if you want to keep the show going for two more years, let me hire more writers."
The situation ended up lose-lose, as Palladino and her husband walked, leaving the show without its unique, quirky voice and Gilmore Girls still needed a horde of new writers to have any shot of mimicking Palladino's trademark voice.