Maybe a fanfiction could focus on how the other characters react to someone using Juggernaut Drive. Some might be in awe, some might be terrified. It could show the different relationships and how they are strained or strengthened in the face of this extremely powerful form.
One idea could be exploring the psychological effects on the character who activates Juggernaut Drive. They might struggle with the newfound power and the loss of control. For example, they could have internal battles between their normal self and the more aggressive, power - hungry side that the Juggernaut Drive brings out.
One interesting feature is the exploration of Issei's enhanced powers. When in Juggernaut Drive, he becomes much more powerful than his normal state. Fanfictions often show him taking on tougher opponents and having more epic battles. For example, in some stories, he can single - handedly defeat high - level devils or fallen angels that he couldn't have before.
Power - up themes are common. The Juggernaut is a very powerful entity in the Highschool DxD universe in fanfictions. So often the stories revolve around the protagonist either obtaining Juggernaut - like powers or using Juggernaut powers in new and exciting ways.
You can give the character a unique backstory related to the Juggernaut Drive. For instance, if they were an experiment gone wrong and that's how they got the power. This would make them stand out.
One popular 'Highschool DxD Issei Juggernaut Drive' fanfiction is 'The Red Dragon's Ascent'. It explores Issei's journey with his Juggernaut Drive in more depth, adding new plotlines and character developments. Another one could be 'Juggernaut Issei: New Powers Unleashed' which focuses on Issei's new abilities when in Juggernaut Drive mode and how it changes his relationships with the other characters in the story.
You can try fanfiction websites like Fanfiction.net or Archive of Our Own. They usually have a large collection of Highschool DxD fanfictions, including those related to the Juggernaut. Just use the search function on the site and type in the relevant keywords.
Maybe Spider - Man's identity is mistaken in the Highschool DxD world. The characters might think he is some sort of new supernatural being. This could lead to a series of comical misunderstandings as he tries to explain his powers and where he comes from while also dealing with the various power struggles and intrigues in the Highschool DxD universe.
One tip is to start with a conflict. It could be an internal conflict within your OC, like struggling with their newfound powers. Or it could be an external conflict, such as a new enemy threatening the peace between the devils, angels, and fallen angels. Another thing is to incorporate the existing Highschool DxD lore. This gives your fanfiction a sense of authenticity. For example, use the different rankings of devils and angels in your plot.
Well, a plot could involve Broly being part of a special program in the Highschool DxD setting. He might be there to learn about controlling his power in a more civilized way. As he tries to fit in, he could befriend some of the main characters from DxD. For example, he could team up with Issei and his friends to compete in some sort of school tournament that has magical and combat elements. This would lead to some epic battles and also some character development for Broly as he learns about friendship and cooperation.
Well, one interesting plot twist is when the Nine - Tails in Naruto is somehow linked to a powerful devil in Highschool DxD. Imagine the chaos and new power - sharing or battling that could occur. It completely flips the script on how we see both the Naruto and Highschool DxD elements. Also, there could be a plot twist where the power - leveling system in Highschool DxD is reversed for Naruto characters, making them struggle in a new way and forcing them to adapt in unexpected ways.
A plot could also focus on a new character who is a hybrid of the two universes. They have the powers of both a devil from High School DxD and a wizard from Harry Potter. They struggle to find their place in either world as they are too different from the norm in both, and they embark on a journey to create their own identity and purpose.