He could have the ability to manipulate the concept of law itself. For instance, he could make it a 'law' that any attack aimed at him misses. This would be like a natural defense mechanism. Another ability could be to set laws on the use of chakra, like 'only I can use fire - style jutsu in this area' which would disrupt his opponents' combat strategies.
Naruto with Law Fruit powers might be able to create laws about time and space in fanfiction. He could make a law that 'time slows down for my enemies', giving him an edge in battle. Also, he could have the power to define the laws of reality. For example, he could make it so that any damage he takes is automatically transferred to his opponent. This would make him a very formidable opponent in the fanfiction world.
Naruto might gain the ability to tap into a primal energy within him due to his wrath powers. This energy could allow him to heal faster when injured in battle. Also, he could have the power to influence the emotions of his enemies. When they look into his eyes during his wrath - filled moments, they could be filled with fear or hesitation. Additionally, his physical attacks could carry a sort of 'wrath - curse' that weakens his opponents over time as they are continuously exposed to his wrath - powered strikes.
One possible ability could be the power to manipulate time. Just like Doflamingo's string powers in One Piece, but applied to time. A character in Naruto fanfiction with this Devil Fruit ability could slow down or speed up time during battles. This would give them a huge advantage, as they could dodge attacks easily or land multiple strikes while the enemy is frozen in time.
One interesting combination could be Naruto's Rasengan with the power of the Pika Pika no Mi (Glint - Glint Fruit). He could create a Rasengan that emits intense light, blinding his opponents as he attacks. Another could be using his Shadow Clone Jutsu with the Mera Mera no Mi (Flame - Flame Fruit). His clones could all be on fire, creating a very intimidating and powerful offensive.
If Naruto had Law Fruit powers in fanfiction, the story would change drastically. He could use the powers to create and enforce his own rules in battles. For example, he could nullify his opponents' jutsu by declaring it 'illegal' within his defined law area. This would give him a huge advantage and change the power dynamics in fights against strong foes like Sasuke or Pain.
He could have the ability to fly by using sonic waves to propel himself. Just like how some characters in other stories use sound to levitate. Another cool ability would be to create sonic shields. These shields could protect him from attacks by vibrating at a high frequency and deflecting incoming projectiles.
In fanfiction, Naruto as a celestial wizard could possess the power of celestial star magic. This type of magic could allow him to use the power of the stars for various purposes. He could create powerful star - based attacks, like shooting star beams at his enemies. He could also use the stars to navigate through different dimensions or gain knowledge about future events, adding a whole new layer of mystery and power to his character.
Maybe Naruto would have the power of cosmic energy projection. He could shoot out powerful blasts of energy that are a mix of his chakra and cosmic forces. This would be a great offensive weapon against the Avengers' enemies.
He could probably gain the ability to phase through objects. Just like wraiths are often depicted as being able to pass through solid things. This would give him an edge in combat and also in sneaking around.
The Sharingan gives the ability to see chakra, which in a Marvel context could be translated to seeing energy or life forces. So they could detect hidden enemies or sense the power levels of other characters. Also, the ninja skills would include things like super - fast movement, stealth, and proficiency with various weapons like kunai and shuriken.
He could have enhanced physical strength and speed. Since he's raised as a weapon, his trainers would focus on maximizing his physical capabilities. Maybe he can move so fast that he's almost a blur in battle. And his strength could be on a level where he can break through solid rock walls with ease. Also, his chakra control might be more precise, allowing him to perform complex jutsu with greater efficiency.