One of the most powerful could be a fan - created character who has the ability to summon multiple Celestial Spirits at once. This would give them a huge advantage in battle as they could combine the powers of different spirits.
Some fanfictions might have a contract where the Celestial Spirit and the wizard can merge their forms. So instead of just summoning the spirit, the wizard becomes part - spirit and gains enhanced abilities.
In Fairy Tail celestial spirits fanfiction, writers get creative with the powers and personalities of the spirits. Some may give a spirit a backstory that wasn't explored in the original. For instance, Aquarius could have a past that involves an ancient water civilization, which adds more depth to her character and her relationship with Lucy.
Another good one is 'Celestial Bonds Renewed'. This fanfiction explores the idea of the celestial spirits' bonds with their summoners being tested in new and unexpected ways. It's full of emotional moments between the characters, especially Lucy and her spirits.
Naruto's ninjutsu like Shadow Clone Technique would be a novelty in Fairy Tail. It's a very different kind of power compared to the magic there. Sasuke's Sharingan - enhanced combat skills would also be distinct. In terms of raw power, Naruto in his stronger forms like Six - Paths Sage Mode could be on par with some of the more powerful Fairy Tail wizards. Sasuke's Mangekyou Sharingan powers would also give him an edge in combat.
One interesting 'Fairy Tail Celestial Spirit' fanfiction could be one where the celestial spirits have to team up to save the spirit world from a new and powerful dark force. They might have to use their combined powers in ways they've never done before.
For creating a Celestial Wizard OC in Fairy Tail fanfiction, first consider their celestial spirits. They could have unique spirits, like a phoenix spirit for fire - related magic. Also, think about their backstory. Maybe they come from a small village where celestial magic was once shunned. Their personality could be shy yet determined, and their goal in the Fairy Tail guild could be to prove the worth of celestial magic.
One idea could be to focus on a Celestial Dragon that has been banished from its own realm and ends up in the Fairy Tail world. It could form an unlikely bond with a Fairy Tail member and learn about friendship and loyalty. Another idea is to explore the origin of the Celestial Dragons in the context of the Fairy Tail universe and how they came to be associated with the Celestial Spirit magic. Maybe a young Celestial Dragon is being hunted, and the Fairy Tail guild decides to protect it, leading to an epic adventure.
There could be many interesting elements in such a fanfic. Maybe it focuses on a new character who has the Celestial Dragon Slayer Magic. This character might have unique powers like being able to slay celestial dragons or absorb their power. They could use this magic to fight against powerful enemies in the Fairy Tail universe.
There are quite a few interesting Naruto and Fairy Tail celestial spirit fanfictions out there. One I remember had Naruto somehow being able to summon Fairy Tail's celestial spirits. It was really cool to see how the different powers from the two universes interacted. Another great one involved the characters from both series teaming up to protect the celestial spirit world which was under threat from a common enemy.