The mainstream is uneasy when it comes to female villains, especially in adventure fiction. Originally, such a character was to be either a
seductress or a
hag or both. Currently, a female baddie is expected to be a dominatrix. She is not to be slain by heroes, especially if she is young and beautiful. If the fiction is gritty, she is to be a victim in her own right.
Male characters are allowed to fill any and every niche of villainy, including seduction. They are the bosses and underlings alike. Some of them are all brain and others all brawn. No act is too dastardly for them. They challenge heroes in dramatic struggles to the death.
Female characters are limited to a very narrow criteria, especially in the villainy of adventure fiction. Currently, they are not allowed to be cowardly in their evil. They must be assertive and of exceptional prowess. Heroines may slay them but heroes are to refrain from doing so. Should a female villain perish at the hands of a male protagonist, her death is to be a momentous tragedy, especially if she is young and beautiful.
Male villains run the entire gamut. Female villains are restricted. It is simply easier to neglect feminine villainy entirely. Woe unto us that such often occurs.
The unwritten rules are not always followed. The mainstream is uneasy when its lines are crossed but forgiving should the offence find favor.
I am a writer of adventure fiction. Many of my villains are female. Some of them are within the narrow perimeters of the mainstream. Others are not. Honestly, I discount the "rules" entirely. My girls are bosses and underlings alike. Some of them are all brain and others all brawn. No act is too dastardly for them. They challenge my heroes in dramatic struggles to the death.
Men and women are different, in both reality and in good fiction. That said, female characters should be allowed to strive and explore in every genre. They should have a place either high or low, good or evil. Let honesty, not policy decide their fate.