Buffy the Vampire Slayer changed television. Not only did it give the world one of the most nuanced female characters in the dark fantasy genre, but it also showed audiences what a bad friend looks like. Xander Harris is the worst. He may be a member of the Scooby Gang, but he's not the kind of person you want in your corner when the world is being swallowed into hell.
Xander isn't bad because he's powerless, or because he has awful fashion sense. He's the worst part of Buffy because he's childish, he can be creepy, and he only thinks about himself. Every other character on Buffy goes through several seasons of character development, with narratives riddled with misfortune, but Xander just becomes more disappointing as the series progresses.
If you're a huge fan of Xander, this doesn’t mean you have bad taste, or that you're watching the show wrong, but there are plenty of reasons why Xander Harris is the worst member of the Scoobies.
When Xander finds real love, he isn't able to appreciate it. Sure, Anya got her start as a vengeance demon and she has less than amiable personal skills, but she loves him and she stands by him. She saves Xander from a disastrous Halloween party, she stays in Sunnydale for Xander, and she puts up with his consistently inappropriate behavior.
Xander and Anya's Nick and Norah Charles routine is cute when they first get together, but by the time they're living together, it's just unnecessary. He talks about Anya's love of money and her blunt attitude to anyone who will listen, but instead of break it off with her, he continues to punish everyone by complaining about her.
The break up finally comes on their wedding day. He's swayed to call things off by a demon pretending to be an older version of himself, and it breaks Anya's heart. As if that weren't bad enough, when Anya hooks up with Spike after she becomes single, Xander flips out as if she still belongs to him.
Everyone has had a friend who has dated someone that's not good for them, whether that person is emotionally unhealthy, physically harmful, or just not a good fit. Most people listen to their friends and give them advice in private, allowing them to make their own decisions. Xander, however, is open with both Buffy and Angel about his disapproval.
After Angel loses his soul and turns into Angelus, he becomes a ruthless slayer in his own right, maiming and feeding on innocent people - and he will do anything to take Buffy down. When Xander finds out that there's a way to get Angel's soul back, his old jealousy returns and he lies to Buffy, saying that there's nothing that the Scoobies can do. Instead, he devises a plan for Buffy to end Angel, clearing the way for him to spend more time with her. Aside from drawing the ire of Angel, Xander never gets his comeuppance for his scheme.
In Season 7, Buffy leads Xander into a trap that gets his eye poked out, and she becomes difficult to deal with while training the new mini-slayers, but that doesn't mean Xander gets to decide where she lives. There's no rule that says he has to work with Buffy - even if they are intertwined by years of vampire slaying - but when he decides he's done with her, he manages to get Buffy thrown out of her own house.
By the end of Season 7, Buffy has some bad ideas about how to take the fight to the first evil, but her poor planning skills don't have a bearing on where she lives. At the very least, Xander should stand behind one of his oldest friends. Instead, he leads the charge in making Buffy homeless.
In the Season 3 episode "Revelations," Xander shows his true colors once he discovers that Angel is still alive, and that he and Buffy have reconnected. Not only does he drop a dime on Buffy to the rest of the crew, but rather than hear her out or let her make her own decisions, he seeks out Faith and enlists her to help with his grudge.
Since Xander is so jealous about Angel and Buffy, he can't understand that Sunnydale needs a supernatural force of good on its side. The thing Xander doesn't realize is that Angel is hiding the Glove of Myneghon, the one thing that Faith's new watcher, Gwendolyn, needs to take over the world.
When he and Faith show up to slay Angel, they distract him long enough for Gwendolyn to grab the glove and nearly wipe out the town. If Xander were capable of putting his personal jealousy behind him, he could have helped to stave off an apocalyptic attack.