* He becomes less of a bully: While still not exactly kind, Dudley becomes much less mean to Harry and shows some signs of remorse for his past behavior. This change is likely due to the events at the Quidditch World Cup, where he witnessed the terror of the Death Eaters and experienced the magic of the wizarding world.
* He starts taking care of his physical health: Dudley's transformation is further evident in his newfound dedication to fitness and health. He starts attending a gym and loses a significant amount of weight. This is likely a result of wanting to change his appearance and feel better about himself, possibly as a consequence of his previous bullying and the events at the Quidditch World Cup.
* He develops a fear of magic: Dudley's fear of magic becomes apparent when he encounters the Dementors guarding Hogwarts. He also shows fear when he encounters the Order of the Phoenix members guarding Harry at the Burrow.
* He begins to appreciate Harry: While not explicit, there are hints that Dudley starts to appreciate Harry more, especially after he witnesses Harry's bravery and courage.
Overall, Dudley's character arc in Goblet of Fire demonstrates that even a seemingly unchangeable person like him can undergo significant positive changes. However, it's crucial to remember that his transformation is far from complete. He still holds onto some of his negative qualities, and his fear of magic might even lead to prejudices against the wizarding world.