Jecht is a non-player character in Final Fantasy X. He is the father of Tidus; legendary Guardian of High Summoner Braska, as well as being a major blitzball star in his hometown of Zanarkand. Jecht is a tall, muscular man with a tendency to drink heavily, and wields a large black sword in battle.
Though he is a good person, Jecht is technically a major antagonist in the game: he forms the core of the current incarnation of Sin, being the most recent Final Aeon to defeat Sin ten years prior to the game, and is seen in Tidus’s mostly negative perspective of him. In person, Jecht only appears in flashbacks and at the very end of the game, but as Sin, he appears throughout the game to attack the party.
On the surface, Jecht is a surly and arrogant man. He frequently refers to himself as “the great Jecht” (Jecht-san in the Japanese releases), and declares himself the best blitzball player there is. As a blitzball star he loves fame and glamour, and asks Braska several times if there will be any celebratory events on their pilgrimage. Eventually his career hit a slump when Jecht began drinking, and it was rumored he was going to retire, though he was quick to deny this and claim he could quit drinking if he chose. Jecht was also verbally abusive to Tidus, giving him the nickname “crybaby” and otherwise brushing him off or berating him.
Despite his numerous flaws, at heart Jecht is a good man. He criticizes Tidus frequently, but does so in the hope his criticisms will encourage Tidus to try harder and disprove him. Jecht does love Tidus, but has trouble expressing it: a sentimental message to Tidus on a sphere is cut off with Jecht mumbling “Remember, you’re my son. And…well, uh…never mind. I’m no good at these things.” When the party reaches Zanarkand, a flashback shows Jecht telling Braska and Auron his dream is to train Tidus into a star blitzball player like him. When Tidus confronts Jecht at the end of the game, his first words to Tidus are to accuse him of being “all bones” and question his diet, but immediately after he compliments Tidus on how much he has grown.
Beyond Tidus, Jecht is generally good-natured. He enjoys the Hymn of the Fayth, and it is the people of Spira singing the tune for him that calms Sin enough for Tidus and his comrades to enter the beast and find Jecht at its core. He is also well-loved by his fans, to the point a blitzball tournament in Zanarkand is named in his honor after he disappears. Perhaps the best example of Jecht’s benevolence is his decision to sacrifice himself to become the Final Aeon, choosing to give up his life and any chance to return home in favor of defeating Sin, and hopefully one day finding a way to defeat it for good.Jecht himself is never fought nor is ever seen fighting. He is only fought in the form of Braska’s Final Aeon, in Sin’s Core. in dissidia jecht has no true interest in serving Chaos, fighting only on the word of the Emperor with the hope of attaining an unspecified dream involving his son. Jecht also confronts Tidus to offer him the chance to settle their grudge and prove himself. Later in the game, it is revealed that Jecht was a member of Cosmos’s ranks during past conflicts between Cosmos and Chaos. His servitude to the God of Discord is simply another component of the Emperor’s grand scheme to destroy Cosmos and end the war.