After 15 years on air, Supernatural has had some standout seasons and some that fall short. While the later seasons might not be the greatest, they still have creative elements. Season 14 focuses on Sam and Dean as vessels for archangels Michael and Lucifer, but lacked fan appeal. Season 15, the show's final season, didn't bring the closure fans wanted. Seasons 12 and 13, while providing answers and expanding on the mythology, didn't sit well with fans.
Season 9 sees conflict among angels, causing the Winchester brothers to go their separate ways.
Season 7 takes the show in a new direction with the introduction of powerful Leviathans. Season 8 delves into the expanded mythology of angels. Season 6 explores Dean's attempt at a normal life and the return of Castiel as an antagonist. Season 10 grapples with Dean's struggle against darkness and introduces fan-favorite villain Rowena.
The first season sets up the deep bond between the Winchester brothers. Season 11 expands on the show's mythology, introducing God's sister as the main antagonist.
Season 2 builds the foundation of the show and introduces important allies. Season 3, although shortened, brings the introduction of Ruby and the idea of Lilith.
Season 4 focuses on Lilith's attempt to break seals and release Lucifer. The best season, according to fans, is the fifth season, which saw the culmination of the original story plan, as the Winchesters try to stop Lucifer and avoid their fates.