Dear Ansem, Xemnas, Xehanort, and technically a bunch of other people.
Could you beat Goku? Or would we need to summon Kingdom Hearts? Could Kingdom Hearts beat Goku?
I don't know anything about the dragon balls
That being said, I got vaporised that one time by Donald Duck, who didn't even have a KEYBLADE.
So, could he beat one Xehanort? Absolutely, apparently anyone can. THIRTEEN XEHANORTS? NEVER!! There is some number of Xehanorts he could defeat, you tell me how many.
Of course he, like anyone else, could be beaten by the power of KINGDOM HEARTS
FILL ME WITH THE POWER OF DARKNESS