Buffy the Vampire Slayer stands out as a foundational genre television series that expertly mixed long-form serialized storytelling with episodic monster-of-the-week mayhem. Buffy survived for 144 episodes across seven seasons and two networks while also spawning a successful spinoff series and comic book continuations and influencing the next decade of supernatural TV shows. Buffy is praised for many reasons, including its stellar cast of unique, inspirational heroes. However, one of Buffy's greatest strengths is its ability to continually create compelling villains who are genuinely intimidating.
Source：https://www.cbr.com/buffy-the-vampire-slayer-best-villains/
