Heinlein’s book Job: A Comedy of Justice shows something similar. The world is a craft project by God - who’d ripped off the basic concept of humanity from Odin - and Satan, named ‘Jerry’ in the story, is just his brother who’s tired of him building and then breaking worlds. Jerry - this turn of the wheel - is the bad guy but it’s clear that in the past he’d been the builder instead.
In the end, it gets appealed to an even higher power who talks to both of them as if they were slightly irritating kids. All is set to rights.
I’m not sure that His Dark Materials entirely fits the bill - but that’s partly because I don’t entirely get all of the boundaries you’re setting in the OP!
(I do love “Satanic” stories that invert the traditional storyline in some way, so I’ll be checking out some of the suggestions above.)
Anyway, SPOILER-filled, vague, and possibly misleading synopsis of HDM:
Heavenly and Satanic forces battle for control of Creation. Neither the so-called Creator nor the Satanic rebels are literal God/Devil figures, just powerful supernatural entities. Through attrition, the victors end up being ordinary human Adam-and-Eve figures.
I always thought that “Can only be killed by…” to be nonsensical. Really?? I mean…did anyone try?? I doubt it. “Hey Gregory!! I seriously doubt Baby Antichrist can withstand an industrial thresher. You don’t have to drag him out to a church* and stab him with a ‘magical dagger’. I mean…how is that even tested??”
*Non-snarky: That scene is crushing. I couldn’t go through with it. Screw you God. I’m not killing a kid I raised as my own even if he isn’t mine.
I don’t think that’s quite it. In the film, Satan is the son of a sort of “anti-God” who exists in an anti-matter universe (conveniently located on the reverse side of a mirror near you). Satan was sent to this universe so he could let his dad in to wreck the place, but got himself sealed in a tin before that could happen. Whether there’s a God of our own universe isn’t entirely clear. There was a Jesus, who maybe helped seal Satan up, and wrote a lot of warnings about what would happen if he got out, but it’s not entirely clear if this Jesus is divine. IIRC, there’s some indications that he might be a space alien.
So, best case scenario is, there’s God and anti-God, and they’re about equally powerful. Worst case (and probably most likely, given the strong Lovecraft influence on Carpenter’s work in this era) is there’s no such thing as the Abrahamic god at all, and the only deity in the film is a Cthulhu-esque monstrosity from outside time and space. But I don’t think the latter situation quite counts as what the OP is looking for.
Well, it works either way.
I suppose one could write several screenplays about someone who looks like Bud Cort being reincarnated as someone who looks like Alanis Morissette.