I was thinking about Idris Elba in Star Trek Beyond and how amazing he was as a supervillain. Alfre Woodard was also magnificent, and of course Orlando Jones takes the cake.
I think you hit the nail on the head when you say white writers don't know how to write Black villains. I think they struggle with nuanced Black characters in general.
That's what made Scandal stand out to me--Shonda Rhimes created a character who was powerful and sometimes monstrous. Olivia Pope was vulnerable and ridiculous and morally flexible, to say the least. She was a fully developed human in a way Black womxn don't get to be, or at least didn't until very recently.
We don't need another hero (heh heh).