Who were one fanfiction in Naruto 9?

Well, it could be a crossover fanfiction where characters from all three universes interact and face common challenges together.

It's hard to say exactly who the Dark One is without reading the fanfiction. It could be a villain from another universe that somehow crosses paths with Naruto. Maybe it's a character with a tragic past that turned to the dark side, and now Naruto has to deal with the consequences of that. It could also be a symbol of all the darkness in the Naruto universe that has been given a physical form to create a more interesting conflict for Naruto.

In 'naruto gets stabbed fanfiction', it might be a new enemy that has emerged, someone with a powerful and unknown jutsu. This enemy could see Naruto as a threat to their plans and decide to stab him to eliminate him. Or it could be a character who has been corrupted by dark power, like a former friend or ally who has fallen to the dark side and no longer recognizes Naruto as a friend.

It could be Sakura. In the original series, their relationship was complex, and in fanfiction, it would be a common choice for her to be the one to dump Naruto, perhaps due to her still having feelings for Sasuke.

It could be a young, inexperienced ninja who accidentally summons Naruto while trying to perform a different summoning jutsu. Maybe they were aiming for a small animal to help them with a simple task, but due to their lack of skill, they end up with Naruto. Another possibility is an enemy of Konoha who wants to use Naruto as a bargaining chip against the village. They think that by having Naruto in their hands, they can force Konoha to meet their demands.

Sakura could be one of the candidates in some fanfictions. Some writers might create such a plot because they want to add drama to the story. Sakura has had a complex relationship with Naruto, and if she cheats on him, it would be a huge shock to Naruto and the readers, creating a lot of emotional turmoil.

Most likely Naruto would be one of the main characters since it's in the Naruto universe and the title seems to imply a focus on a single character's story, which in this case is probably Naruto.

In many of these fanfictions, you might find popular characters like Naruto, Sasuke, Ichigo, and Rukia crossing paths. But it varies a lot based on the author's imagination and story direction.

Maybe Kakashi could still be his mentor. Even though One for All is a new and different power, Kakashi is very experienced. He could help Naruto understand how to incorporate this new power into his overall combat strategy. Kakashi would be able to analyze the power and give Naruto advice on how to train with it while still relying on his ninja skills.

Sasuke could be a likely candidate. He's always been somewhat jealous of Naruto's growth and popularity. In the stress of the Forest of Death, he might let that jealousy get the better of him and betray Naruto. Maybe he thinks that by getting rid of Naruto, he can be the only strong one in the team.