The outcast or loner who gets caught up in the clan war. They don't have a natural allegiance to any of the clans, but they might get involved for various reasons, like helping a friend in one of the clans or having their own agenda. Their unique perspective and lack of traditional clan loyalty could make them stand out as an interesting character.
Another plot twist could be a character from one clan who discovers they have a long - lost family member in another clan. This could completely change their loyalty and the dynamics of the war. For example, they might try to stop the fighting between the two clans to protect their new - found family.
Naruto himself would be really interesting. Imagine him trying to understand and adapt to the samurai way of life. His energetic and determined personality would bring a lot of humor and action as he clashes with the more traditional samurai values at first, but then finds common ground.
I think Pikachu and Graystripe would make a fun pair. Pikachu's cute and energetic nature could contrast with Graystripe's more laid - back but still adventurous self. Also, Brock and Tallstar could be an interesting duo. Brock's knowledge of healing and Tallstar's wisdom could lead to some great conversations and collaborative efforts in the crossover story. And let's not forget about Team Rocket's Jessie and a sneaky rogue Warrior. They could plot together or end up competing in their own devious ways.
A character who has the power to see the future of the Keyblade War could be really interesting. They would know the outcome of certain battles and events, but be unable to change them directly. This would put them in a moral dilemma, especially if they see friends or allies about to be defeated. They could try to influence the war in indirect ways, like giving advice that seems cryptic but is actually meant to guide the other Keyblade wielders. Their presence would also make other characters question whether fate can be changed or if everything is already predetermined in the context of the Keyblade War.
I think Obito could be really interesting. His complex backstory and his role in the war were so crucial. You could explore his internal struggle further, like his lingering feelings for Rin and how that influenced his actions during the war in more depth.
I think Ryo of the Ronin Warriors and Sailor Mars could be an interesting pairing. Ryo is hot - headed and powerful, and Sailor Mars is also strong - willed and has fire - based powers. Their personalities might clash at first but then they could learn to respect each other's abilities and work well together.
I think an original character could be a great villain. Maybe a rogue ninja who has mastered a unique and forbidden jutsu that allows him to control the minds of others. He uses this power during the war to turn allies against each other, and Naruto has to figure out how to stop him without harming his friends who are under the villain's control. This villain could have a tragic backstory that led him to this path of destruction.
It could be an original character. For instance, a ninja from a small, unknown village who has a unique power and is forced to participate in the war. They could be the underdog that everyone underestimates at first.
A character who is initially very meek but transforms into a vengeful force could be fascinating. For instance, a bullied student who finally snaps and decides to take revenge on the bullies in a very calculated way.
Loki in a cartoon Infinity War fanfiction could be a fascinating focus. He's so full of mischief and trickery. You could show his internal struggle between his desire for power and his loyalty (or lack thereof) to his brother Thor in a more cartoony, over - the - top way. Maybe he teams up with the heroes against Thanos in the most unexpected way, all while plotting his own schemes on the side.