Chuck's Endings

Lilith reveals to Dean that Chuck has a "perv-y" obsession with the Winchesters and that everyone of his endings end the same way -- one brother killing the other.

Endings

Demon Blood Ending

An alternate ending in which Sam embraced his demon blood addiction and went full Dark Side, becoming the general of the demon army as Azazel intended. In this ending, Sam had killed Bobby and Jody, forcing Dean to pursue him with his own band of hunters, which included Benny Lafitte. After confronting Sam in the Bunker, Dean has his neck psychically snapped by his brother.

Episodes: 15.01 Back and to the Future and 15.04 Atomic Monsters

Samifer Ending

An alternate ending where Lucifer was successful in possessing and maintaining control of Sam. Dean attempts to kill Lucifer using the Colt, shooting Sam in the back of the head. The Colt does not work, and Lucifer is easily able to heal the bullet wound in his head before burning Dean alive.

Episodes: 15.05 Proverbs 17:3

Mark of Cain Universe

An ending where Dean has given into the Mark of Cain. After a one-sided fight where Sam attempts to talk Dean down, a Knight of Hell version of Dean picks Sam up by the neck and flashes his black demon eyes before stabbing his brother with the First Blade and killing him.

Episodes: 15.05 Proverbs 17:3