The problem is that you can't simply just say that, you need facts, you need stats. When you compare two different worlds you need to have some kind of proof instead of just randomly blurting out something like that.
The fact is that KH is a much bigger place than FF.
The fact that it's a much bigger place than FF means that when something is "top ranked" in KH, it will be greater than something "top ranked" in FF. Due to being on a larger scale.

As I've told you, stats are worthless and don't matter.

How do you know that just because Xemnas was the most powerful in his multiverse he's more powerful than someone like Kefka? ExDeath?
Now you're just plain ignoring my posts. Xemnas was "most powerful" on a larger scale than Kefka or ExDeath. That's why.
That's insane, and that's not how someone goes about reaching that kind of conclusion.
No, using gameplay stats like HP to judge plot strength is insane when they have nothing to do with each other.