There are indeed Naruto fanfictions where he has Ultra Instinct. Fanfiction writers like to experiment with different power combinations. By giving Naruto Ultra Instinct, they can create really exciting battle scenes. For example, Naruto could use Ultra Instinct to dodge attacks more effectively during a fight with a powerful enemy like Madara, adding a whole new dimension to the story.
It could be a rogue ninja who has also discovered a dark version of the ultra instinct. This ninja uses his power for evil, like taking over villages and enslaving people. He would be a major threat to Naruto and his friends because his power is so similar yet so different from Naruto's ultra instinct - like powers.
One idea could be Naruto discovers a hidden ancient jutsu that unlocks his ultra instinct - like powers. He then uses these powers to quickly defeat enemies in the Fourth Great Ninja War, surprising everyone including Sasuke. Another could be Naruto training in a secret dimension where he gradually attains ultra instinct and has to face off against a new, powerful and unknown enemy that threatens the entire ninja world.
You could write a fanfiction where Goku teaches others about Ultra Instinct. Maybe he tries to pass on this power to Gohan or Trunks. This would involve Goku having to understand the power more deeply himself in order to teach it, and it would also be a great way to develop the other characters.
One popular one is 'Naruto: The Ultra Instinct Awakening'. In this fanfiction, Naruto discovers his Ultra Instinct during a life - or - death battle. It has great descriptions of his new power and how it affects his fighting style.
A fanfiction could focus on Goku's relationships while in Ultra Instinct. For example, how does he interact with his friends and family? Does Vegeta view him differently? In this story, Goku might struggle to control the Ultra Instinct around his loved ones because it makes him seem so detached. This could lead to some interesting emotional moments between the characters.
Well, it depends on the author's imagination. Some fanfics might show ultra instinct as an overwhelming power, while others might have a more nuanced take.
Well, with Ultra Instinct, Goku would be able to react extremely quickly to the DC heroes' powers. For instance, when facing Flash, who is super fast, Goku in Ultra Instinct might be able to match his speed or even anticipate his moves better. This could lead to a mutual respect between them as they test each other's limits.
One idea could be an Ultra Instinct Goku crossing over with the Dragon Ball Super universe and the Naruto universe. He could end up in Konoha and use his Ultra Instinct to sense and counter the attacks of the ninja there. Maybe he'd even have to fight some of the powerful ninjas like Naruto or Sasuke in a friendly sparring match to test their skills against his new form.
That really depends on personal preference. However, some popular ones often have a great balance between action and character development. For example, stories that explore how Goku's relationships change after getting Ultra Instinct can be really engaging.