Warning: Major Supernatural spoilers ahead!
Supernatural fans are pretty upset about the Season 15 episode titled "Despair." A key character died, but it's not his death that's bothering people, per se — it's the intent behind his death that's frustrating. Castiel sacrificed himself for Dean, and gets absorbed by The Empty. Why did he sacrifice himself? Because Castiel was in love with Dean and that was part of the deal with the Entity. The moment he confesses how he feels, he gets killed off.
What happens is: Billie ends up knocking on the bunker door, threatening to kill Cas and Dean. Cas figured he can stop this from happening by essentially taking his own life. Previously Cas made a deal with the Entity: Cas lets the Entity take Jack's place only if Cas agrees to live his life until the very moment