The biggest problem with Godzilla In Hell's powerscaling stems from two things; the story's lack of dialogue, and multiple writers in a comic book with only five issues, and it's the lack of dialog that led to a lot of people asking the authors a lot of questions.
The story is almost 100% abstract (not least because that was the intention from the start if I'm not mistaken, even taking ideas from The Divine Comedy when Godzilla descended into Hell). It's the personification of nuclear terror traveling through different pockets of hell, conquering not only his enemies and obstacles, but himself at the end of the story, but that's the thing, it's almost entirely visual. We have brief narrations at the beginning of each issue (or not even that), or when God-Mountain shouts for Godzilla to submit, or when he goes through an N situation (for example, when he tricks Ghidorah and Destoroyah into destroying one of the walls of hell that was blocking his destination), nothing complex. It's one of my favorite IDW stories, but when it gets into the powerscaling business, that's where things get complicated, especially for those who are puritanical about visual feats.
I personally separate the good apples from the bad, I think it's wrong to say that every WoG based on this story is disposable, because for a story with almost zero narration, everything depends on our interpretation (which is what David Watcher wanted in the last issue). The problem is that people focus too much on superfitial questions and answers. Like, "wow, can Godzilla nuke the whole IDW megaverse?", or "wow, is Godzilla omniscient and omnipresent?".