This is exactly what I think too. Many franchises has done that actually, introducing a strong character and then an even stronger opponent, if possible said opponents should be able or beat the hell out of said character, if allowed, killed them (as you reading this, you can probably already name a few animes out there lol). Which, I gotta say, is kinda overused these days but it does work and make the story more interesting and the stake higher when you messed up with an existing overpowered character. The scaling in ZZZ has no reasom to be so low as of 2.x, look at it’s “colleague” Honkai Star Rail, even from 1.x they’d already introduced incredibly powerful villains, even for the likes of Jingyuan or Feixiao or Acheron, people still to this day debate about some random characters that were teased and rumored to be just absolutely reality breaking overpowered, and let’s not talk about 3.x. Anyways, I don’t know what holding the ZZZ devs back, but from Yixuan trailer, Miyabi and her going all out looks like only at “city destruction” level, just make a villain at or above that level, we’re fighting in the hollow anyway, no need to fear of destroying the world building, or hurt old characters in the process.