Friends of WF
You're limiting antagonists to human beings. Antagonists need not be human beings -- need not even be persons. An antagonist may have no head or thought process to get inside of.IMO you're in danger of creating a batch of two-dimensional characters, as was most of the Star Wars cast.
Yes, pure evil exists - or at least from my perspective, but someone else might see my bad guys as not so bad or possibly even good... Hitler and Stalin would be a stretch for anyone though... however, even those tyrants believed they were in the right.
So, I ask that you consider looking inside your antagonist's head to see their motives. Why are they doing these harmful things? The exercise might give your character greater depth and make them more interesting.
IMO Star Wars is a great fairy tale/myth. But even stories that lean into realism can have non-person or non-human antagonists. Some horror comes to mind, as well as Jack-London-style man-vs.-nature tales.
Til We Have Faces is quite nuanced, but even then, there is the goddess Ungit. Certainly, she is more of symbol, but you can't discount the antagonist/villain role she plays in the story. Descent Into Hell has a batch of nuanced, very human "bad guys," but there's also Lillith. And Lillith is Lillith, and that's okay. She doesn't need to be humanized for the story to work. In fact, humanizing her would ruin what the story needs to be.