John Winchester Dies To Save Dean\n\n Supernatural season 2, episode 1, "In My Time of Dying," opened with Dean in a coma. Desperate to save his son's life, John summoned Azazel and made a deal with the demon  he sacrificed his life and soul so Dean would live.

John Winchester plays a driving force in Supernatural's early days, but his role as a recurring character was severely limited after the beginning of Supernatural season 2 when John was killed by the demon Azazel.