The biggest difference is the creativity of the fanfiction writers. In the anime, the fight follows a set storyline. But in fanfiction, anything can happen. For example, Naruto could suddenly gain a new power that was never in the anime. It's like a whole new world of possibilities.
Konan could be really interesting. In some fanfictions, she might have a different backstory or motivation that affects the Naruto vs Pain fight. For example, she could be secretly trying to stop Pain from going too far in his destruction of the Leaf Village.
Kabuto could also be a good antagonist. After he gained all those powers and knowledge, he might target Naruto's six - tails form. He could use his medical ninjutsu to try and manipulate Naruto's transformation or even try to extract the power of the six - tails for his own use. Since he has the ability to mimic other ninja's techniques, he could be a formidable foe against Naruto in six - tails form.
One possible outcome could be Naruto winning through his unwavering determination and newfound powers. He might use his Sage Mode combined with the power of the Nine - Tails to outwit the Ten - Tails.
In such a fanfiction, Naruto might have to use all his skills. He could start with his Rasengan. The Nine - tails Clone would be strong with its own Tailed Beast powers. Naruto would probably try to outwit it rather than just use brute force.
It's hard to say. Naruto has a lot of experience and powerful jutsu. But the Nine - tails Clone has the brute strength of the Nine - tails. However, I think Naruto would win in the end. He has shown time and time again that he can overcome seemingly unbeatable opponents.
Sasuke would be a likely ally. They have a long - standing relationship and have fought side by side before. Sasuke's Sharingan and his own unique abilities would be a great asset against the Ten - Tails.
It's hard to say for sure. If the fanfiction focuses on Hinata's growth, she could potentially defeat Pain through her own skills and some unexpected twists. But Naruto is also likely to be a major factor, so it could be a combined effort of both of them that overcomes Pain.
In this fanfiction, Naruto might be extremely enraged seeing Hinata in danger against Pain. Hinata, on the other hand, would likely show her newfound strength and determination. Maybe she'd manage to land a few surprise attacks on Pain before Naruto fully jumps into the fray.
Well, the Naruto vs Pain fight in the original series is epic. Fanfiction allows fans to explore different scenarios and what - ifs. Maybe they want to see different character developments during that intense battle.