Harry Potter is definitely one of the most popular. Since he is the main character in the original series, fans often like to give him a second chance in various scenarios. Hermione Granger is also popular as she is so intelligent and fans might want to see her make different choices with a second chance. Another popular character is Draco Malfoy. His complex character and his family's situation make him an interesting choice for a second - chance story.
Harry himself is of course very popular as the story revolves around his second chance. Hermione is also often a key character as she can help Harry with her knowledge and planning. Another popular character is Dumbledore. His wisdom and guidance are crucial in many fanfictions, and in the context of a second chance, he can play an even more important role in mentoring Harry.
Gandalf is surely a popular character in such fanfiction. His wisdom and powerful magic would make him a central figure. He could be the one guiding the characters from both universes on how to deal with the new threats that emerge from the crossover. Hermione is also popular. Her intelligence and knowledge of magic could be very useful in this new combined world, and fans love to see her solve problems.
Harry Potter himself is often a popular character in these fanfics. After all, the idea of him having a second chance at things is very appealing. Hermione is also popular as she could use her intelligence in different ways with a second chance. And Draco Malfoy is quite popular too. People like to explore his character getting a second chance to break free from his family's expectations and become a better person.
The protagonist is often a popular choice. Their journey through time and the decisions they make can be explored in great depth. Also, any character with a mysterious past can be interesting. For example, a character who seems to know more about the time - related phenomena than they let on. Their backstory can be delved into and new storylines can be created around them.
Albus and Scorpius are extremely popular. Their friendship and the unique dynamic between them, with Albus being a Potter and Scorpius being a Malfoy, offers a lot of room for exploration. Writers can delve into their insecurities, how they support each other, and how they deal with the expectations placed on them because of their families.
James Potter is often a popular choice. He's the leader of the Marauders, a talented wizard, and his relationship with Lily Evans is a major draw. His transformation from a bit of a troublemaker to a more responsible person is also an interesting aspect to explore.
Sasuke is also very popular. Fans love to explore what would happen if he had a second chance to redeem himself or make different choices regarding his path of revenge. He has a complex character, and in these fanfictions, there are a lot of possibilities for his development.
In addition to the main couples, Techno is a character that can be a focus. He's such a fun and relatable character. Fanfics could center around his friendships with the others, or even a love interest for him that we didn't see much in the series.
Dudley can also be a fascinating character to write about. You could show his growth from a bully to someone who might start to understand Harry. Maybe he has a secret admiration for Harry's magical abilities.
Definitely Harry Potter himself. He is the main character in the original series, and in fanfiction, his relationship with the Weasleys can be explored in many ways, like his bond with Ron as his best friend and his relationship with the Weasley parents as a sort of surrogate family.