May 16, 20196 yr Roxas has had some pretty tough fights under his belt that's he's come out on top. The many Heartless he defeated while a part of the Organisation, boss mode Xion, non-darkness Riku, Axel (when Roxas is under a lot of confusion) all within a year. It takes a lot to knock out Roxas, and very few actually achieve it in-story. Sora's battle with Roxas at Memory Skyscraper in Kingdom Hearts 2 Final Mix can be brutal if you aren't prepared, and can be tougher than the rest of the Organisation bosses depending on how you play. In a one on one, even playing field, I'd odds on Roxas.
June 2, 20196 yr Roxas can literally solo Saix in KH3, and you can watch the whole thing from the sidelines, all you have to do is land the finishing blow. None of the other Org13 fights are like that. To be fair, Saix isn't a top tier villain like some of the others, but I think it's clear Nomura wants everyone to know that Roxas is a complete savage.
Time for the battle of the best bois, who's better: Roxas or Sora?