In fanfic, Cedric Diggory is usually depicted as having a strong sense of fairness. This is evident in how he competes in the Triwizard Tournament. He also has a certain grace about him. He moves through the halls of Hogwarts with confidence and poise. His academic abilities are also a common trait. He's often shown as being quite good at his studies, especially in areas like Transfiguration and Charms.
One common trait is his kindness. He's always shown as a nice guy in fanfic, just as he was in the books. Another is his courage. He doesn't shy away from challenges, like the Triwizard Tournament tasks. And his loyalty, whether it's to his friends or to Hogwarts, is often emphasized.
Cedric Diggory in Harry Potter fanfic is often characterized by his humility. Despite his popularity and good looks, he doesn't let it go to his head. He's also known for his sense of honor. When it comes to competing, he plays by the rules. His social skills are another aspect. He gets along well with most students at Hogwarts, regardless of their house, which is a trait that fanfic writers like to play up.