The Supernatural series should have ended after season 5 for five reasons. Firstly, the series creator's original plan was for only five seasons. Secondly, the storyline's cohesiveness in the first five seasons was unmatched. Thirdly, the crafting of supernatural storylines that are both implausible and relatable was challenging.

Fourthly, the themes of family, sacrifice, free will, and destiny were satisfactorily explored in the first five seasons. Finally, the climactic showdown between Michael and Lucifer, with the latter possessing Sam's body, was the perfect ending. Sam and Dean's character arcs were fully developed, and the final battle was a battle of biblical proportions, making the human victory all the more gratifying.