The prophecy of The Prince That Was Promised favors Jon Snow. After all, Jon is a Targaryen male, and he spent years fighting bloody battles and forging his reputation as one of the greatest warriors in the Seven Kingdoms. Jon also shared a unique animosity with the Night King after several face-to-face confrontations. However, Jon was not the one who ultimately killed the Night King. Meanwhile, Daenerys’ dragons were crucial to beating the White Walkers. Jon ended up murdering Daenerys out of fear that she was becoming a Mad Queen. Yet together, Jon and Dany appear to be the Song of Ice and Fire, but it’s left ambiguous by Game of Thrones if either or both are supposed to be The Prince That Was Promised.
Ultimately, it was Arya Stark (Maisie Williams) who killed the Night King at the end of The Long Night. Arya, who was trained by the Faceless Men to become an assassin, used Aegon’s Valyrian steel dagger to destroy the Night King. The dagger, also known as the catspaw dagger, has a dark tie to Arya’s family as it was once meant to kill her brother, Bran Stark (Isaac Hempstead-Wright).
Arya’s killing blow to the Night King could mean she is the surprise incarnation of The Prince That Was Promised. There are hints that this is the case, especially after Melisandre (Carice van Houten) told Arya of her vision to kill those with brown eyes, green eyes, and blue eyes. However, Arya has no ties to Aegon Targaryen’s bloodline, which seems to disqualify her as The Prince That Was Promised as prophecized by Aegon.