An old sage from a hidden part of the ninja world. This sage could have been in seclusion for centuries, observing the world from afar. He decides to come out and teach Naruto because he sees the potential in him to bring about a new era of peace in the ninja world. He would bring with him ancient techniques and a different way of thinking compared to the current ninja system.
Jiraiya could be a candidate if he were somehow made immortal. He already has a deep connection with Naruto and has taught him a great deal. His knowledge of Sage Mode and other jutsu could be further expanded if he were immortal, and he could continue to guide Naruto for a much longer time.
Kurenai could be a great strict teacher in a Naruto fanfic. She is a jonin and has experience in teaching. Her skills in genjutsu could be used to create strict training scenarios for Naruto. Also, Asuma could be a candidate. He is known for his straightforwardness. In a fanfic, he could be a strict teacher, making Naruto focus on his combat skills and strategy more. He could be tough on Naruto, expecting high standards from him.
Naruto himself would be an obvious choice. He has the strength, the popularity among the villagers, and the experience from all his adventures. He would bring a new energy and a more inclusive approach to leading the village.
Anko Mitarashi could be a good candidate. She's strong -willed and has her own set of skills. Her somewhat wild personality could contrast well with Kakashi's more reserved nature. They could have met during a mission and over time, developed feelings for each other.
The plot could involve the immortal teacher passing on ancient and powerful jutsu to Naruto. For example, the teacher might know a unique form of chakra control that Naruto can use to enhance his Rasengan. This new knowledge could make Naruto stand out even more in battles against strong opponents like Sasuke or the Akatsuki members.
One good candidate could be a powerful sage. Sages in the Naruto universe are known for their wisdom and great power. If he was Kaguya's husband, he could have taught her many things about chakra and the world before she turned bad. This would add an interesting backstory to Kaguya's character and also create new plotlines about the origin of chakra in the Naruto world.
One good candidate could be an original character. For example, a powerful kunoichi from a small, peaceful clan. She could bring a different perspective to Madara's life. Another could be a character from another ninja village, like a Kiri ninja who was sent as a diplomat and ended up falling for Madara.
There could be a 'immortal naruto fanfic' where Naruto's immortality leads him to explore different dimensions. In these adventures, he meets versions of his friends and foes from alternate realities and has to find a way to either help or stop them, depending on the situation. This would add a whole new level of excitement and mystery to the Naruto universe.
Luna Lovegood could be a great candidate. She has a unique perspective on magic and the wizarding world. Her kind and open - minded nature would make her a loving and protective godmother. She could teach Harry about the magical creatures she loves so much and also help him see things from different angles when he's facing difficult situations.
One great 'Naruto Godlike Teacher Fanfic' is 'The Teacher Who Transformed Naruto'. It has an interesting plot where the teacher uses unique methods to train Naruto and his friends, making them much stronger in ways that are different from the original story.