I think Kakashi would be really interesting. Imagine if he had the Ope Ope no Mi (Op - Op Fruit). He could use his Sharingan to analyze and then use the fruit's powers to perform complex surgeries or manipulate the battlefield in ways that no one else could. His strategic mind would be able to come up with really unique ways to utilize the powers of the Akuma no Mi in combat and non - combat situations.
Sasuke. If Sasuke had an Akuma no Mi power, like the Goro Goro no Mi (Rumble - Rumble Fruit), it would make him even more formidable. He could use lightning - based attacks from his ninjutsu in combination with the electrical powers of the fruit. His already brooding and powerful character would become even more complex and dangerous.
Naruto would be an obvious choice. If he had the Hito Hito no Mi (Human - Human Fruit), Model: Nika, which gives Luffy his rubbery and super - strong abilities in One Piece. Naruto could use his already incredible physical strength and add the unique properties of the fruit. He could stretch his limbs to reach far - off enemies or perform acrobatic maneuvers that would be really entertaining to see. His positive and energetic personality would also bring a new flavor to the use of this power.
Harry Potter himself is a likely candidate. Given his heroic nature and the need to constantly fight against dark forces, an Akuma no Mi could be a great addition to his arsenal of skills. It would give him new ways to protect his friends and defeat his enemies.
One interesting concept could be how the powers of the Akuma no Mi would interact with the ninja abilities in Naruto. For example, if a character had a Logia - type Akuma no Mi, like the Mera Mera no Mi (Flame - Flame Fruit), they could use it in combination with fire - based ninjutsu to create more powerful attacks. Another concept might be the clash of values between the One Piece world where the Akuma no Mi exist and the Naruto world. In the Naruto world, they value things like teamwork and honor in a different way compared to the pirates in One Piece.
One interesting concept could be the combination of the magical world of Harry Potter with the unique powers of the Akuma no Mi from One Piece. For example, a character might use a Devil Fruit power in a wizarding duel, creating a whole new dynamic of combat. It could also involve characters from Harry Potter having to adapt to the rules and limitations of the Akuma no Mi powers in their own universe.
One interesting 'akuma naruto fanfiction' could be about Naruto facing an akuma - like demon that has unique powers. Maybe the demon has the ability to manipulate time, and Naruto has to find a way to overcome this new and powerful foe using his own skills and the help of his friends. Another story might involve Naruto being possessed by an akuma and his friends having to find a way to save him without harming him.
In some 'Naruto Akuma' fanfictions, Akuma could be a mentor figure to Naruto. Since Akuma has his own set of unique and powerful abilities, he could teach Naruto different combat techniques or ways to tap into new sources of power. This would change the dynamic of Naruto's growth and his relationships with other characters in the series.
I think Sasuke would be really interesting. He already has a dark and brooding personality, and adding the power of the Magu Magu no Mi would make him even more formidable. He could use the magma to enhance his sword attacks, creating a molten blade or use it to create traps for his enemies. His Sharingan could also be used in combination with the magma powers to anticipate his opponents' moves better and launch more precise attacks.
Harry Potter himself is often a popular character in these fanfictions. Writers might explore how he would react to Akuma - related threats. Hermione is also popular as she could use her intelligence to understand and combat Akuma - like phenomena. Another popular character could be Draco Malfoy, perhaps being involved in Akuma - influenced dark magic plots.
Naruto himself could be the main character. Imagine Naruto getting his hands on the Mochi Mochi no Mi. He would likely use his new powers in a very exuberant and creative way. His ability to make mochi could add a whole new dimension to his combat style, like using mochi to cushion his falls during his high - flying attacks or creating mochi - walls for defense.
I'm not sure if there is a specific fanfic exactly like that. There are so many Naruto fanfics out there, and while some might involve Naruto having an interest in Akuma in some creative crossovers, it would take some serious searching through fanfic platforms to find one.
Luka is another character that shows up a lot. His calm and understanding nature, along with his relationship with Marinette, provides a contrast to the more chaotic aspects of akuma attacks. His love for Marinette, whether it's unrequited or reciprocated, can be a central part of the fanfiction. He might also play a role in helping Marinette deal with her feelings for Adrien while akumas are causing trouble in their lives.