ComicBook recently conducted a subjective selection of "One Piece" characters, choosing Luffy, Ace, and Roronoa Zoro as three representatives of courage. The selection primarily considers the characters' endurance of pain, protection of companions, and performance when facing lethal risks; it is not an official ranking or power level list.
Luffy's inclusion is related to his experiences of continuing to fight after sustaining severe injuries multiple times. In the Alabasta arc, he was defeated twice by Crocodile, enduring being pierced by hooks and severe dehydration, before finally winning in their third encounter. Later, he was severely injured by Magellan's poison and underwent costly treatment. During the Marineford War, Akainu's magma attack left a massive X-shaped scar on his chest.
Ace's inclusion centers on his final actions during the Marineford War. Knowing he might not survive, he still stepped in front of Luffy to take Akainu's attack, and in his final moments, expressed gratitude to Luffy and his companions. The author thus views his choice to protect his comrades as a significant demonstration of his courage.
Zoro's experiences include being imprisoned and starved upon his first appearance, as well as later suffering severe injuries at the hands of Mihawk. During the Thriller Bark arc, he willingly took on all of Luffy's pain. Despite Kuma warning that this choice could be fatal, Zoro did not hesitate and ultimately survived.