Godwinson
"Well, I've got nothing."
Sabrina can, at any instant, sterilize all potential for life as we know it within an area that expands outward at the speed of light, indefinitely. She can do this without witching out, without intrinsically killing herself, and frankly it doesn't even cost much Grief. She can also scale down to "merely" sterilizing the entire solar system, or "merely" blowing up the planet, or even down to just burning the surface or blowing up an entire city.Sabrina's abilities are very much the kind of thing that would be horrifying to face on a villainus magical girl.
Like pretty much instant 'hero killer' territory if the user isn't offed before they can do anything.
Thankfully not 'only the author can save them now' levels of busted but still waaaaay beyond the typical antagonist.
It is, in fact, one of the hardest things Sabrina can do, to take down an opponent without dealing lasting harm. She has an excessive overabundance of combat lethality, to the point that further work on it is a matter of recreation.
There were many other issues that went into it than that, and more that came up well after it ended. Also, frankly, Worm sucks.Honestly, I think you gave up too soon. Sabrina's story isn't about whether she'll win any given fight, because she almost definitely will. The question is what the consequences of that victory will be, and how bad the collateral turns out. As was noted above, the greatest threat to her is really herself.