There could be young ninjas who look up to Sasuke. They might be orphans of the war, and Sasuke takes them under his wing. These new characters would bring fresh energy and new storylines as Sasuke mentors them.
There could be characters from other anime or manga universes. For instance, characters from 'One Piece' might show up. Luffy could be a really interesting addition as his carefree and adventurous nature would contrast with Naruto's more serious and duty - bound personality.
Naruto is often paired with Sasuke. Their bond is so strong that in post - war fanfictions, they are usually shown working together to rebuild the shinobi world. Sakura is also a common character paired with Sasuke. Since she has feelings for him, in these fanfictions, she might be trying to get closer to him and help him heal from his past traumas.
One potential new character could be a mysterious figure from another dimension who appears in Peter's world after Endgame. This character could have unique powers and a complex backstory that ties into the post - Endgame chaos. Also, there might be a new journalist character who is trying to expose Peter's identity, adding a whole new layer of drama to his life. There could also be a new mentor - like figure for Peter, someone who has a different perspective on being a hero compared to Tony Stark.
A potential character could be a reclusive old wizard who lives on the outskirts of the wizarding world. This wizard might have his own reasons for living in seclusion, but when he sees Harry's loneliness, he takes him under his wing. Another character could be a young, orphaned witch who is also trying to find her place in the post - war wizarding world and she crosses paths with Harry.
Sakura might develop into a more confident and assertive person. After the war, she has proven herself as a strong kunoichi, and with Sasuke by her side, she could grow even more. Sasuke, on the other hand, would develop by learning to trust and love again. He has been through so much, but with Sakura's love and support, he could become a more stable and caring person.
Sora could be a main character as he is often central in the Keyblade universe. His determination and pure heart would make him a key figure in the war. Another could be Riku, with his complex character and his own journey of growth and redemption.
Maybe the OC is a wizard from a different magical culture. For example, he could be from a far - flung wizarding community that was not directly involved in the war but has unique magical abilities. Neville could also be an important character, perhaps collaborating with Harry and the OC on projects to revive the magical plants that were damaged during the war.
Sasuke might become more empathetic. After the war, he has seen the destruction and pain it caused. With Sakura by his side, he could learn to express his emotions better. Sakura, too, could become more confident. She has proven herself during the war, and now she can continue to grow, especially in her relationship with Sasuke.
A wise old owl could be a new character. This owl could be the one who actually has knowledge about the real threats (or lack thereof) in their world. Maybe he tries to guide Chicken Little and the other animals. Another potential character could be a mischievous squirrel. The squirrel could be constantly causing small troubles that make Chicken Little think the sky is falling all over again. For example, it could knock down acorns that make loud noises.
A wise old sea turtle could be a new character. He could be the one who gives the mermaid advice about the human world and warns her of the potential dangers.