In a crossover with 'The Flash', Barry Allen could be a character. He could be injured in a fight and end up in Shaun's hospital. Shaun would have to deal with Barry's super - fast metabolism while treating his injuries. And Barry could also learn a thing or two about perseverance from Shaun as he recovers.
Well, from 'Supernatural', Sam and Dean Winchester could be involved. They could bring in a case where they suspect a supernatural cause for a patient's illness. Shaun would be skeptical at first but then start to see things in a new light as they investigate. It would be a mix of the medical and the supernatural worlds.
If we consider a crossover with 'Stranger Things', Eleven could be a character in the fanfiction. Maybe she has some kind of medical mystery related to her powers. Shaun would have to figure out what's going on with her while also dealing with the strange events that seem to follow her. It would be an interesting blend of science - fiction and medical drama.
The Arbiter is another character. Given his complex relationship with the Covenant and his newfound alliance with the UNSC in the Halo series, his perspective would add depth to a crossover story. He could provide valuable insights to Noble 6 about the Covenant's inner workings and help in diplomatic situations if needed.
Naruto himself would be a key character. His relationship with Kakashi is a central part of the original story, so seeing how he reacts to an evil Kakashi would be fascinating. Sasuke could also be involved. He and Kakashi have a complex relationship, and an evil Kakashi might try to manipulate Sasuke further for his own dark purposes.
One popular character could be Goku from Dragon Ball. His power levels and his journey towards becoming stronger could create an interesting dynamic with the god of destruction. Another might be Thanos from the Marvel Universe. Thanos' quest for balance through his own extreme means could have some parallels or clashes with the god of destruction's role. And of course, characters like Harry Potter could also be involved. Imagine the magic of the wizarding world coming up against the raw power of the god of destruction.
Obviously, Ichigo would be one of the main characters. He brings his unique set of powers and personality to the crossover. Ruby Rose could also be a central figure. Her leadership and scythe - wielding skills could interact with Ichigo in various ways, perhaps in combat or in making decisions for the group.
Another potential character could be Naruto. Naruto has his own set of ninja powers and a strong will. If he were in a crossover with Vegeta, their different ideologies about power and friendship could clash or they could learn from each other. Naruto's ability to never give up might inspire Vegeta in some ways, or Vegeta's raw power could amaze Naruto.
In this fanfiction, characters like Luffy from One Piece might be involved. Luffy's carefree yet determined nature would contrast with Ichigo's new god - like presence. Also, characters from the Bleach universe itself could have new relationships with Ichigo. For instance, Aizen might see Ichigo's godhood as a threat or an opportunity, leading to a complex plot development.
Superman from the DC universe. Superman stands for truth, justice, and the American way, but his methods are often more lenient compared to Akainu. The two could have a philosophical debate about justice while also having to fight a common enemy.
Luffy from One Piece would be a great crossover character. His carefree and determined nature would contrast well with Naruto's own. They could both bond over their love for their friends and their strong wills. Another good character could be Harry Potter. Imagine Naruto in the wizarding world, and he and Harry could exchange knowledge about their respective magic systems, with Naruto showing off his ninjutsu while Harry demonstrates spells.
The Doctor from Doctor Who would be an amazing crossover character. He could arrive in his TARDIS right in the middle of the wedding preparations. He could then use his knowledge and skills to solve any problems that arise, like a strange alien invasion that targets the wedding. His time - traveling abilities would also add an extra layer of excitement to the story.
Well, in this type of fanfiction, Hermione could also be an important character, but in a different light. Maybe she tries to stop an evil Harry, or perhaps she is corrupted by him and becomes his accomplice. Other characters like the White Witch from Narnia could be involved. Her icy magic and cold - hearted nature could be an interesting contrast or complement to an evil Harry's powers. And don't forget about characters from other YA dark fantasy series, such as the Darkling from Shadow and Bone, who could potentially cross paths with an evil Harry.