No, that would be too easy. We're going with this one!
Yes, it's Diana from V, V: The Final Battle, and the series V that lasted only a single season on NBC back in the 1980s. Diana was the show's main villain, and she was truly rotten to the core. Played with relish by Jane Badler, Diana never had, to my recollection, so much as a second of repentance or any kind of flash of good behavior. No Darth Vader-esque deathbed conversion for her; Diana was the show's Hitler. (Although that's probably not the best analogy, since she was a military leader and not a head of state.)
Here's Diana being all evil and stuff:
In retrospect, I'm not sure how well V holds up. The central SF-nal premise is deeply silly; these aliens have come from across the Galaxy to steal all of Earth's water, under the notion that water is a very rare commodity. Even given that it was the early 1980s, I think we knew at that point that water was more common than that; just a couple of years later, Arthur C. Clarke's 2010: Odyssey Two made a key plot point out of the enormous amounts of water ice on Europa. It's just awfully hard to believe that these aliens can build interstellar FTL starships that are three miles in diameter, but can't figure out how to feed their people or come up with water.
And the characters are pretty much all stock characters, every one of them, right down to Diana, who could be a fascinating character to explore – what would the aliens' ethics be, that they're perfectly willing to slaughter a sentient species for food? Alas, this is never explored, in favor of action and derring-do. Which is all pretty fun to watch, it must be admitted. Diana herself is as one-dimensional as villains get. She doesn't even get to seem terribly intelligent; her main defining traits seem to be visceral loathing for humans and utter ruthlessness in getting what she wants.
But she's still really memorable, at least for me, because Jane Badler played her wonderfully.