It could be about Naruto finding an ancient and powerful phylactery during one of his adventures. Maybe he accidentally activates it and has to deal with the consequences, like strange spirits being released. He then might use his ninja skills and quick thinking to contain the situation and learn more about the phylactery's origin and purpose.
Shikamaru would probably be the most vocal against it. He's a lazy but intelligent character. He would see Naruto's plan as too troublesome and dangerous. He'd tell Naruto that there are too many unknowns and that it's not worth the risk. He might even try to enlist the help of Kakashi or other more experienced ninjas to stop Naruto from going through with it.
A phylactery in the context of some fictional lore is often associated with dark magic and immortality. In a fanfiction where Harry Potter makes a phylactery, it could be a very dark turn for his character. Maybe he's been corrupted by the idea of never dying after facing so many near - death experiences. It could also mean that he's delved into some really old and dangerous magic that he doesn't fully understand. This could lead to a story where he has to grapple with the moral implications of creating such a thing, as well as deal with the reactions of his friends and the wizarding world at large.
The wizarding world would be in an uproar. Phylacteries are associated with dark magic. Harry is seen as a hero, and for him to create a phylactery would shatter the image. The Ministry of Magic would likely brand him as a dark wizard or at least someone who has strayed too far from the light. His friends would be divided. Some might try to defend him, believing there was a good reason, while others would be horrified and distance themselves.
In some fanfictions, Naruto might be feared due to his overwhelming power. For example, if he has some new and extremely dangerous jutsu that others can't understand or counter. It could also be because he has changed his personality to be more cold - blooded and less forgiving, which is a departure from his original kind - hearted self in the official story.
Well, in such a fanfiction, Naruto might be unkillable because of some special power-ups. Maybe he has some kind of indestructible chakra shield that constantly protects him from any harm. It could also be due to a unique bond with a powerful entity that grants him immortality. Another possibility is that his willpower is so strong that it literally defies death, allowing him to survive any fatal situation.
In fanfiction, Naruto can be considered a prodigy often because of his unique abilities. For example, his natural talent for learning new jutsu quickly. He might also show extraordinary leadership skills from a young age, which sets him apart and makes him seem like a prodigy.
The power system in Naruto is one factor. The idea of chakra and how it can be manipulated in various ways is quite experimental. It allows for a wide range of abilities and combat styles. Also, the character arcs often deviate from typical hero - villain dynamics. For example, some characters have complex motives that are not simply good or bad.
In fanfiction, Naruto can be made invincible by changing the rules of the Naruto universe. Maybe the author decides that there are no limits to how much he can train or that he has a special bloodline trait that no one else has. Also, if the author decides to remove all his enemies' advantages, it can make Naruto look unbeatable.
Well, one thing that makes a Naruto fanfiction funny is when the characters are put in out - of - character situations. For example, if Naruto, who is usually brave, suddenly becomes extremely cowardly in a comical situation. Another factor is the use of humor in dialogue. When the characters say witty and sarcastic things to each other, it can be really funny. Also, when the author takes a normal Naruto scenario and twists it in a completely unexpected and absurd way, like making the chakra system work in a really strange and humorous way.