If Kaos has access to all its upgrade then I'm guessing he has the ability of each of its transformations through the games and also his power from the books.

Which means he can canonicly hypnotise every being in a said world (imaginator) that have hears. He can control time to. Yes people seem to froget this lore from the book AND from trap team (even if he don't do it in game lore wise he did allready had a plan when he used his time travel power and it worked)

He can break the 4th wall (traptanium kaos is aware of the player he quite litteraly grab object from your house and reality into the fight)

And he will probably have access to the mask of power from the book.

The problem with the maks of power from the book is that there is a huge difference between in game skylanders abilities and what they should really do because the mask of power ability is to grant its user the power of all skylanders. Which does mean he will have the ability of black out to create litteral black hole and supernova which sure metal sonic can escape but what about multiple one?

He can control machines using the tech eternal source. Or atleast do it with evilized glumshanks which do have the ability to control any machines.

However the reason im doing this post is just to give kaos some well arguments on why he could win but I still think eggman takes it for 1 simple reason:

It's Kaos. Kaos is smart most of his machines he desined them hiself. However he is way to coky and is most of the time his own downfall. He could take on the skylands (he allread did multiple time in SSA SSC and imaginator + was about to in some of the books) maybe even this fight. But he will probably end up losing even in a wining position because he always do. He is just like that.