In this thread, a person more powerful than every FF character

[PuPu]

Suffice to say that Xemnas is not all-powerful. He does not possess universal power

KH is God. Xemnas absorbs God. Xemnas becomes God. If you're going to make claims like this, you might want to try to find things to back up your claims.

(not even worth mentioning the fact he didn't absorb a complete KH),

Which isn't that different from Kefka supposedly absorbing "All Magic" except for the few Espers that the party controlled. The thing is, there's still the scale difference.

Within this KHverse, actually "defeating" darkness requires one to be wielding a Keyblade

...no it doesn't. Defeating Heartless requires Keyblades, but it doesn't mean that other dark beings such as Jafar and Ursula can't be defeated as well. I don't even know what you mean by "defeating darkness" anyways, since it's not like you're "defeating water" by defeating Demyx.

a weapon which only four characters possess (if you include Kairi),

TAV
SRK
Mickey
Master Xehanort
Master Eraqus
Vanitas
Xion
Roxas

That's a lot more than four, dude.

this not representing the perpetual strength of the original KH characters (or lack thereof in FF characters represented therein) but instead denoting the power within their hearts which marked them to be chosen by the power of the Keyblade.

Power and strength come in many different forms, dude.

I'm not implying that Sora having the ability to defeat Heartless while the FF characters couldn't means that he's more powerful than them. Because he still beat other powerful enemies in the game which didn't require the Keyblade to beat. (Maleficent & friends, Organization XIII, etc.)

At this point, the only thing that you're saying is "Well KH power is invalid because it's different from the form of power in FF" yet you still can't prove why you think it's invalid.

And even if what you said IS true, it doesn't matter at all. Sora is still has more power than any FF character, since he beat an enemy more powerful than any enemies that the FF characters have faced in their respective universes. You can argue that Xemnas didn't truly have universal power all you want, because even if it were true, he still has more power than any FF villain + FF power source due to scale. It honestly doesn't matter where Sora's power came from, the fact is: it's still his own power.

Also, you act like "power of the heart" is the only power that exists in the KHverse.