Yuna

A central character of both Final Fantasy X and Final Fantasy X-2 (also makes a cameo in Kingdom Hearts 2). She lived as a Summoner on Besaid, then left with Tidus, along with her other Guardians, including Lulu, Rikku, Kimahri, and Auron and eventually initiated the Final Summoning to banish Sin. Normally, a summoner doesn't survive this, but Tidus was killed in her place. Also, Sin is not banished for the normal 10-year period know as a "Calm", but is banished forever, making Yuna famous as the High Summoner who brought about the "Eternal Calm". In the next installment, Yuna is a Gunner with Rikku and Paine as part of the Gullwings. She is troubled by Tidus and refuses to believe he is dead. In KH2 she is a Heartless spy for Maleficent and eventually gives you the Gullwing keyblade.