While Xehanort ruined everyone's life, Terra got it the worst, and should be the one to defeat and kill Xehanort. He has the more personal grudge against Xehanort. Sora didn't even know of Xehanort's existence until KHII, and Terra dealt with way worse than Sora. Let's see...
-Master Xehanort sabotaged the MoM, and convinced Eraqus that Terra used darkness, and didn't deserve to be a master. It caused Terra to go into one hell of a depression.
-Master Xehanort manipulated Terra throughout the entire game, and caused him to turn against Eraqus, Ven, and Aqua
-Master Xehanort called Terra "Master Terra" as a way to mess with him
-Master Xehanort killed Eraqus, Terra's father figure in front of his eyes
-Master Xehanort destroyed Terra's home in front of his eyes
-Master Xehanort freezes Ven right in front of Terra, while he is helpless and can do nothing about it
-Master Xehanort lost the fight against Terra purposely, and then possessed his body
-Terra is almost completely helpless in his own body now because of Master Xehanort
-For the next 11 years Terra is trapped in his own body probably watching Master Xehanort destroy the worlds, and he can do nothing but watch
Come on...Terra should be the one to kill Xehanort.
-Master Xehanort sabotaged the MoM, and convinced Eraqus that Terra used darkness, and didn't deserve to be a master. It caused Terra to go into one hell of a depression.
-Master Xehanort manipulated Terra throughout the entire game, and caused him to turn against Eraqus, Ven, and Aqua
-Master Xehanort called Terra "Master Terra" as a way to mess with him
-Master Xehanort killed Eraqus, Terra's father figure in front of his eyes
-Master Xehanort destroyed Terra's home in front of his eyes
-Master Xehanort freezes Ven right in front of Terra, while he is helpless and can do nothing about it
-Master Xehanort lost the fight against Terra purposely, and then possessed his body
-Terra is almost completely helpless in his own body now because of Master Xehanort
-For the next 11 years Terra is trapped in his own body probably watching Master Xehanort destroy the worlds, and he can do nothing but watch
Come on...Terra should be the one to kill Xehanort.