Final Battle (Final Fantasy X)

"Final Battle", also known as "Decisive Battle", is the theme that plays during the final boss battle against Yu Yevon in Final Fantasy X, composed by Masashi Hamauzu. It is the eighteenth track on disc 4 of the game's original soundtrack. The song is a 3-part variation and the third part (2:20-2:40) is infused with the melody of Hymn of the Fayth.

Piano Collections: Final Fantasy X
The Piano Collections version is mostly faithful to the OST version. There is a second version found in the Piano Collections Book under "Special Presents", and has an added staccato section.

Final Fantasy X Vocal Collection
The beginning of track 12 "Spiral" contains a short and simplified piano solo of the song and then enters an irrelevant electronic-rock fusion.