Maybe Naruto has a secret jutsu that he has been developing in the fanfiction. He unleashes this jutsu on the Akatsuki, which incapacitates most of them at once. Then he uses his taijutsu skills to take down the remaining members one by one. His speed and strength, enhanced by his chakra, would be crucial in this scenario. He could also use his ability to sense chakra to predict the Akatsuki members' movements and attacks, giving him an upper hand.
Han Solo is a very prominent one. His solo adventures before joining the Rebellion are full of action and character - building moments. Another is Luke Skywalker. His solo training and quests are key to the overall plot. And as I mentioned before, Princess Leia has her own important solo moments as well.
Sure. '127 Hours' is a great solo adventure movie based on a true story. It tells the story of Aron Ralston's harrowing experience of being trapped in a canyon. Another one is 'The Pursuit of Happyness' which is based on Chris Gardner's real - life struggle as a single father trying to make it in the business world.
Maybe it's because she's often seen as the most talented singer in the show. Writers of fanfiction might just go with that perception and give her all the solos.
The SCP Foundation is purely fictional. It's a collection of imaginative and often creepy stories and characters that are made up for entertainment purposes and have no basis in reality.