A possible crossover in the fanfic could involve the Titans being created as a result of some dark magic related to the Seven Deadly Sins. The characters from the Seven Deadly Sins universe might come to the Attack on Titan world to stop this dark magic from spreading further. Levi could learn a thing or two from Ban's immortality or regeneration abilities, which could make him even more of a formidable fighter against the Titans.
Well, in a fanfic, Eren Yeager could be seen as having a struggle with one of the Seven Deadly Sins, like Pride. His determination to free his people could tip over into excessive pride. And the characters from Seven Deadly Sins could introduce new fighting styles and strategies to the Survey Corps. Maybe Meliodas' full counter ability could be taught to some of the more skilled soldiers in Attack on Titan.
Levi from Attack on Titan and Meliodas from Seven Deadly Sins both have strong leadership qualities. They would probably either clash due to their different leadership styles or find a way to work together really well. Levi is more stoic and strict, while Meliodas is more laid - back but still very determined. Their combined leadership could be really interesting in a fanfic.
One interesting crossover could be the magic from Fairy Tail interacting with the powers of the Seven Deadly Sins. For example, Natsu's fire magic might combine with Meliodas' full counter in a really cool way during a battle against a common enemy. It could create a whole new kind of attack that is both powerful and visually stunning.
In a Naruto x Attack on Titan fanfic, there could be a situation where the ninjas are brought into the world of Attack on Titan. Naruto himself could use his rasengan against Titans, which would be a very powerful weapon. The characters from Attack on Titan might be intrigued by the ninja's ability to use chakra and try to learn from them. This could lead to a new kind of training regime within the walls, where they combine their existing combat skills with the newfound chakra - based techniques.
One interesting crossover could be exploring how the characters from Naruto would react to the concept of the Seven Deadly Sins. For example, Naruto's determination might contrast with Sloth. Maybe Naruto would try to inspire the slothful characters in the Seven Deadly Sins world. Another aspect could be how Sasuke's thirst for power might be related to Greed. It would be fascinating to see how the ninja skills from Naruto blend with the magical elements of the Seven Deadly Sins universe.
Well, a great crossover would involve Hulk. Just imagine Hulk going berserk on the Titans. He could easily take them down with his brute strength. Then there's Black Widow, her combat skills and stealth could be used to gather intelligence on the Titans. Also, Hawkeye's archery skills could be useful in hitting the weak spots of the Titans from a distance. These crossovers would make for an exciting fanfic.
A fanfic idea could be to have the Seven Deadly Sins lose their powers and have to learn to rely on their wits and each other in a more human way. This could lead to character development as they face challenges without their supernatural abilities. Also, a story about a new character who is influenced by all the seven sins at once and has to struggle to find their true self in the midst of all that chaos.
One interesting crossover could be the Autobots and Decepticons getting involved in the fight against the Titans. The Autobots' advanced technology could be used to create new weapons or defenses against the Titans. For example, their energy shields might be able to withstand the Titans' attacks. Another aspect could be the Transformers' ability to transform into different forms being used in strategic ways within the walls. Maybe a Transformer could transform into a large structure to block a Titan's path or into a flying vehicle to scout for Titans from above.
One idea could be creating an OC who is a descendant of one of the Seven Deadly Sins. For example, if your OC is related to Meliodas, they could inherit some of his power but also have their own unique abilities. Another idea is to have an OC who is on a quest to overcome the influence of the Seven Deadly Sins in a world where their presence has corrupted society. They could travel around, facing challenges related to each sin and learning valuable lessons along the way. Also, an OC who is an apprentice to one of the Sins, learning their combat skills and moral code, would be an interesting concept.
One interesting plotline could be their journey to overcome the various challenges in the world of Seven Deadly Sins while also dealing with their own relationship. For example, they might face powerful enemies together and in the process, their bond grows stronger. Another could be a story that focuses on their past lives and how it affects their current relationship.
One interesting crossover could be the Titans invading Hogwarts. The students would have to use their magic in new and creative ways to defend against the massive Titans. For example, they could use spells like Wingardium Leviosa to lift debris and block the Titans' paths, or use the Patronus charm to create a powerful force that might stun or repel the Titans. Another aspect could be the characters from Attack on Titan learning about magic. Eren might be intrigued by the power of magic and try to incorporate it into his fight against the Titans. He could potentially team up with Harry Potter and his friends to find a new way to defeat the Titans once and for all.