What episode does everone think Luffy die?

Everyone believes Luffy dies in "One Piece" during the "Marineford War" arc, specifically in Episode 483, titled "The Return of the Captain." In this episode, Luffy is gravely injured and seemingly loses his will to fight after witnessing the death of his brother, Ace. The emotional impact of the scene leads many characters, and viewers alike, to fear for Luffy's fate, although he ultimately survives. This moment serves as a significant turning point in the series, highlighting the stakes and the deep bonds between characters.