The film isn't afraid of tragedy; the cursed fate of Will Turner adds a weight that later sequels lacked.

If you meant something else by "best" (best scene, best quote, best character in that movie), let me know and I'll narrow it down

Unlike the first two films, which focused on personal curses and debt, At World's End elevates the conflict to a global scale. The East India Trading Company, led by the cold and calculating Lord Cutler Beckett, is systematically eradicating piracy. The stakes aren't just about a chest of gold or a beating heart; they are about the very soul of the ocean. Seeing the "Pirate Lords" from the four corners of the earth unite for the Brethren Court gives the film a sense of historical and mythological weight. 2. Hans Zimmer’s Career-Best Score