30 Day SF & Fantasy Challenge Day 22: The Best SF Villain

We’re dipping into the science fiction side of the well today to talk about our favorite villains there. Good villains are hard to find and ones that retain that feeling over the years even more so. For many, Darth Vader still holds as one of the best out there, particularly for mainstream audiences. But we’re The Avocado so we’re going to go beyond the mainstream, right? So today, we want to know from whatever medium you prefer, to hear about your favorite villains that run through the fantasy landscape.

Bonus Question: Which SF villain failed to live up to their potential?