There’s really no reason for people to be so defensive/aggressive over this King stuff.
The biggest part of the Zoro fight against King was figuring out how the abilities of a Lunarian work, and figuring out how to exploit them. Zoro does it two ways: by timing when King switches modes and by increasing his attack power such that it’s strong enough to hurt King in fire mode. Once he had this down, the fight ended very quickly.
If Ryokugyu knows how Lunarians work already, he can take King down very fast. If his attack power surpasses the threshold of King’s fire mode, he can take him down very fast.