A resident of Zanarkand, Jecht is Tidus' father. Overconfident to the point of cockiness, Jecht is a man of many flaws, being loud, brash, stubborn, and arrogant. Still, under the rugged exterior lies a much kinder core. Jecht is good natured, puts others before his own well-being and is always on hand to offer his aid. He's a bundle of contradictions, simply put: if you get past the arrogance, he's actually a nice guy.
Ten years prior to the start of the game, Jecht was pulled into Spira. Thinking himself mad, he quickly gets drunk, only to be thrown into prison. It's at this point Braska, a summoner, recruits him, to be his Guardian. Along with Auron, Jecht accepts. Braska succeeds in his endeavours to bring the Calm to Spira, but it's not without sacrifice...
As a result of offering himself to become Braska's Final Aeon, Jecht becomes Sin. His plans to defeat Sin from the inside fall short, so he brings Tidus to Spira to try to make up for that short fall.
Jecht is one of the final bosses of the game, and can be considered to be the overall antagonist due to the fact he is Sin, though as it is Yu Yevon pulling the strings, that in itself is debateable. Really, he's something of an antihero...
He really is one of my favourite characters in the franchise. He puts himself through a lot to make up for his shortcomings: he tries his hardest to make things right. He's arrogant, and even if he does have the wrong methods when it comes to Tidus, his heart is very much in the right place. He's a well rounded character and he definitely deserves a fanlisting of his own.
Hymn of the Fayth
The hymn is something Jecht particularly enjoys; as Sin, it's the only thing that can calm him. After disregarding the temporary name, I always knew this would be the replacement. ^