Yes, there are likely some fanfictions out there with such a concept. Fanfiction writers often come up with creative crossovers. You can try searching on popular fanfiction websites like Archive of Our Own or Fanfiction.net.
Maybe in the fanfiction, Naruto discovers Killua's world and is in awe of Killua's lightning - based abilities. He then tries to learn from Killua to enhance his own Rasengan or other jutsu. Also, it could involve the two of them teaming up against a common enemy that threatens both their worlds.
His abilities would likely cause quite a stir. Killua's ability to move at high speeds and his combat skills would make him a formidable opponent in the Naruto universe. Maybe he'd be seen as an outsider at first, but as he proves himself, he could be respected. His nen - based attacks could be misinterpreted as some strange new jutsu that the ninja haven't seen before. He might even team up with some of the more adventurous ninja like Naruto himself and go on wild adventures.
Yes, there are some. You can start by looking on fanfiction websites. Some authors might create stories where they draw parallels between Naruto and Killua, perhaps in terms of their growth, their relationships with friends, or their unique abilities.
The theme of growth is also prevalent. They both start as somewhat naive boys and grow into powerful and more mature individuals. In 'naruto is like killua fanfiction', you might see how they influence each other's growth, for example, Naruto's positive outlook might affect Killua's more cynical view at times, and vice versa.
Eventually, Naruto could grow resentful. If the ignoring persists for a long time, he might start to think that Kakashi doesn't care about him at all. This could change Naruto's attitude towards Kakashi and might even make him more rebellious in his training or actions. However, deep down, he still probably hopes for Kakashi's recognition and approval.
Naruto would probably be extremely hurt. He has always considered Hinata a friend and perhaps more. Betrayal from her would be a huge blow to his trusting nature. He might initially be in denial, not wanting to believe that Hinata could do such a thing.
At first, Naruto would be completely shocked. He has always seen Hinata as a loyal friend and someone who has deep feelings for him. So the idea of her betrayal would be hard to fathom. He might try to deny it at first.
He would probably be very angry. Naruto has always been a free - spirited person, and being experimented on against his will would be a huge violation of his rights. He might initially try to resist physically, but as the situation gets more complex, he could start to plot his escape and revenge.
He would be filled with rage. Naruto has a strong sense of justice and the fact that someone took Hinata away from him would fuel his anger. He would vow to find and punish whoever was responsible. He might even become reckless in his pursuit of vengeance, endangering himself and those around him. His friends would have to step in to try and bring him back to his senses.