In the world of One Piece, there are countless ways to become a powerful fighter. Scientific advancements, Devil Fruit abilities, and unique techniques like the World Government's Six Powers are all viable options in combat. However, those who want to one day conquer the entirety of the Grand Line must first master one thing: Haki. Haki is essentially spiritual power that exists within every character in One Piece, but very few are able to consciously control and wield it.
Source：https://www.cbr.com/one-piece-straw-hat-haki-users/
