4) Becoming (Parts One and Two) – Season 2, Episodes 21 And 22
By now, it’s probably become clear that Buffy is home to some of the best season finales in television – it did originate the idea of the season-long story arc, after all. It’s a tough call, but the finest of the lot has to be season 2’s “Becoming.” There are many reasons for this, but ultimately it’s the best because of the personal connection to Buffy, as she has to fight her former lover for the sake of the world.
“Becoming” also includes two hugely significant moments that would go on to change the show, namely Buffy’s mother Joyce finding out that her daughter’s the Slayer and the first time that Buffy teams up with Spike – foreshadowing his later turn to the good side.
The most enduring part of the two-parter, though, is the heartbreaking climax, as Buffy is forced to send Angel to hell, even though he’s finally got his soul back. It’s not all about kicking ass and quipping when you’re a superhero. Sometimes you have to make terrible choices for the greater good.