Tapion said:
Now that I think about, South Kaioshin scales to God-Tier by default, since he must be stronger than Sealed Dai Kaioshin via Shin's statement, and Sealed Dai Kaioshin is the one who, with a fraction of his power (the vast majority of it had been permanently destroyed when Pure Boo was defeated), beat the crap out of weaksauce Moro.
We never saw the battle's conclusion beyond Dai Kaioshin using the Kai Kai Matoru, so the framing would suggest that's what ended the fight rather than it dragging on after that. I'd chalk it up to the technique causing Moro to become fatigued and 10 million years being more than enough time to recover some of his magic.
In fact, it's quite likely that the strongest Kaioshin and the Hakaishin are meant to be equal in power.
Despite Zamasu > All Kaioshin at the time of Super.
Elder Kaioshin established that Beerus was weaker than the current Boo 75 million years ago; Dai Kaioshin was absorbed 5 million years ago
Chapter: 479 (DBZ 285), P6.5, P7.2, P8.2-3
Elder Kaioshin: “That’s ri~~~ight. Lo~~~ong, lo~~~ong ago, there was this ridiculously strong and ba~~~ad dude. Well, not as much as this Majin Boo guy now, but still~~~. He did it, he se~~~ealed me away inside that sword. Me here. He was freaked out by how fearsome I am. Yep, sure wa~~~as.”
Whilst you could interpret that as Beerus beig both not as strong or bad as Boo, the Steve Simmons translation of the anime points to only the latter.
Episode 250, 12m33s - 12m44s
Elder Kaioshin: "Long Long ago, y'know, there was this terribly strong, y'know, bad guy, y'know. Well, not as bad as this Majin Boo now."