Roxas because he's stronger than Base Sora, who I'm sure could beat Auron. Nobodies are stronger than their human counterparts. Auron has the powerful limit Bushido and has several overdrives such as Dragon Fang, Banishing Blade, and Tornado. Roxas has reaction commands and Sora's abilities are pretty much Roxas's as well. Remember when you had to play as Sora, all the abilities you learned from Roxas transferred to him, so Roxas's and Sora's abilities are the same, at least without Drive Forms. With all of Auron's abilities and magic from Final Fantasy X, it would be more of a close fight. I still think Roxas would win since he has reaction commands and has some badass moves of his own. Anyway, here's my ratings for both.
Roxas: 53%
Auron: 47%
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Maybe we'll meet again... Wandering Flame (one of the best pieces in the Final Fantasy X soundtrack)
Yeah Auron seems pretty badass in KH2 since he did all his overdrives at once...and he does all those aerial attacks and moves really fast in KH2. But, he's based right off of Final Fantasy X, so it's obvious he's equally as strong. I like how he said in that one scene "This is my story and you're not part of it." It reminded me of that one part in Final Fantasy X where he was taking Tidus into the portal or whatever. Also in the end of KH2 during the credits, you see Auron changing into pyreflies just like he did in the end of Final Fantasy X. Square Enix is awesome.
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Maybe we'll meet again... Wandering Flame (one of the best pieces in the Final Fantasy X soundtrack)