One way to write good Thor fanfiction without adult content is to explore different aspects of his mythology. You can delve into the stories of his hammer Mjolnir, its origin and powers. Maybe write a story where Thor has to retrieve Mjolnir from a new and dangerous place. Also, think about how Thor would interact with different cultures in the Marvel universe. Incorporate elements of Norse mythology and blend them with the modern - day Marvel setting to create a unique and interesting fanfiction.
To write good Thor fanfiction without adult content, focus on his relationships with other characters. You could write about his bromance with the Hulk or his mentorship of a young Asgardian warrior. Use vivid descriptions of Asgard's landscapes, the battles Thor fights, and his internal thoughts and emotions. Also, add some humor to the story, like Thor being confused by Earth's modern technology. By doing these things, you can create a great Thor fanfiction.