Well, one characteristic is the expansion of Harry's abilities. In these fanfictions, he might develop new spells or magical skills that make him a more formidable champion. Also, the relationships in 'champion Harry Potter fanfiction' can be different. His friendships with Ron and Hermione might be tested or strengthened in new ways. And often, the fanfiction will have a more in - depth look at the political and magical society within Hogwarts and the wizarding world, which affects Harry's journey as a champion.
In some fanfictions, the Durmstrang champion could have a backstory that involves a conflict between the values of Durmstrang and those of Hogwarts. They might struggle with the more lenient rules at Hogwarts compared to the strict and often dark - arts - friendly environment at Durmstrang. This internal conflict could add depth to their character as they compete in the tournament.
Well, it often explores the idea of heroism in a new way. The concept of a 'champion's champion' allows for a more extreme and glorified version of the heroic journey we saw in the original Harry Potter series.
A plotline might be centered around the relationships between the characters in the fanfiction. The champion's champion could form unexpected alliances or romances. Maybe they team up with a Slytherin who has been underestimated, and together they break the stereotypes of their houses while trying to achieve a common goal in the wizarding world.
There is 'Champion's Champion: The New Trials'. This fanfiction takes the concept and adds new magical challenges and adventures for the characters. It also has an interesting plot where the champion has to face some ancient magic threats that were not explored in the original books.
Hermione Granger is another potential main character. Her intelligence and quick thinking would be invaluable in any competition or quest in the fanfiction. She could be the strategist behind the 'champion's champion', guiding them with her vast knowledge of magic and spells.
Often, there are antagonists as well. It could be a dark wizard who is trying to disrupt the champion's tasks for his own evil purposes. This antagonist might have a grudge against Hogwarts or the wizarding community in general. He could be using dark magic to create obstacles for the champions, making their journey full of danger and excitement.
It could be about Harry Potter becoming a champion in a world related to the gods. Maybe he has to face god - like challenges or prove himself worthy in a realm ruled by deities.
I'm not sure of a specific one off the top of my head. But you can look on fanfic websites like Archive of Our Own. There are likely many 'a champion harry potter fanfic' there that have been highly rated by other fans.