attackfish

I wonder if there is a greater percentage of female villains in YA - maybe that's related somehow to the evil stepmother archetype in fairy tales. Disney's got Maleficient but also Cruella de Ville. Harry Potter's got Bellatrix Lestrange, but also Umbridge (though Umbridge, too, seems to prefer to be a sidekick). Sarah Cross's Dull Boy has a female villain. Rick Riordan's Olympus books have male and female villains, but in the newer series Gaea seems to be more powerful than any of the gods and must be kept asleep. In the Mythos Academy books, Gwen Frost's main enemy seems to be female (a classic Mean Girl type).

I can't think of many more offhand, but then not all stories have villains at all.