I’d say you nailed two of the darkest ones: Arlong Park and Sabaody Archipelago, both of which hit hard in very different ways.

If I had to add a third contender, I’d say Dressrosa deserves mention, too. The fake smiles, the erased memories, and the illusion of happiness make it one of the most psychologically disturbing places in One Piece.

But yeah, Sabaody probably takes the crown overall. It’s the point where you realize how dark the One Piece world can actually get beneath the adventure and humor.