You actually solved a huge problem with scaling regarding Post-Training Chainsaw Man and his Post-Weakening keys.
Previously, since Chainsaw Man was depowered, we assumed him to be on a level weaker than his Pre-Training key, hence why he is Building level, upscaling from the Cockroach Devils building level feat on his Post-Weakening key.
However, the scaling was placed to question as the mere mass of the Cockroach Devil was able to crush the Bat Devil and kill it. His death being all due to a strike from Post-Weakening Chainsaw Man.
Scaling wise, the Bat Devil is scaling to Pre-Training Chainsaw Man in durability being able to take a strike from him to the jaw. We had to mark the defeat of the Part 2 Bat Devil as an outlier as it would contradict Chainsaw Man's weakening.
But now that we can confirm that Post-Training Chainsaw Man's true AP potential is 8B+, makes us able to place him just somewhere at "At least High 8-C" regarding his scaling above the Bat Devil in Part 2.