In Final Fantasy IV, the dark knight who becomes a paladin is Cecil Harvey.
Cecil begins the game as the captain of Baron’s Red Wings, an elite air force of dark knights. Although he is loyal to King Baron, he increasingly questions the morality of the kingdom’s orders, especially after the theft of Mysidia’s Water Crystal. His unease becomes a central part of the game’s story rather than merely background characterization.
After being stripped of his rank, Cecil travels to Mount Ordeals. There, he confronts the darkness within himself and proves his willingness to protect others. Completing the trial changes his class from Dark Knight to Paladin, giving him a brighter appearance and access to white magic. The transformation is both a gameplay change and the defining redemption arc of Final Fantasy IV.
Cecil is sometimes confused with Kain Highwind, his childhood friend and fellow soldier, or with Golbez, a major antagonist connected to him. Neither becomes the game’s paladin protagonist: that role belongs specifically to Cecil.