Sometimes, a really good plot twist in these fanfics is a character's role reversal. For instance, a usually heroic character from Resident Evil becoming a villain in the presence of Devil May Cry's chaotic and morally ambiguous world. Or vice versa, a devil hunter from Devil May Cry being forced to work for the bad guys in the Resident Evil universe due to some complex situation. This can create a lot of tension and interesting character development.
One exciting plot twist could be a character from Devil May Cry suddenly losing their powers in the Dead or Alive universe and having to rely on the skills and fighting styles of the DOA characters to survive. For example, Dante might find that his devil trigger doesn't work as expected, and he has to learn the acrobatic and martial arts moves of Kasumi or Hayabusa to face the new threats in this strange crossover world.
Perhaps a plot twist where one of the main Avengers, like Captain America, is actually a reincarnation of a hero from the Devil May Cry world. This would bring in a whole new backstory for him. He would start to show abilities related to Devil May Cry, like being able to sense demons or having enhanced sword - fighting skills. It would also create a conflict within him as he tries to balance his newfound identity with his role as an Avenger.
One common plot twist could be Poison Ivy using her powers in a new and unexpected way to either help or hinder Batman. For example, she might be able to control a new type of plant that has properties that can nullify Batman's gadgets. Another could be a situation where Batman has to make a difficult choice between saving Gotham and saving Poison Ivy from some greater threat. This would put his moral code to the test as he has always seen her as a villain but may have developed some complex feelings in the context of the fanfic.
Some fanfics explore the idea of relationships between characters from the two franchises. For instance, there could be a romantic relationship between a character from Devil May Cry and one from Resident Evil. This can add a whole new layer of complexity to the story. It could also lead to interesting situations where characters have to choose between their loyalty to their own franchise's world and their newfound relationships. For example, if a Devil May Cry character falls in love with a Resident Evil character, they might have to decide whether to stay in the Resident Evil world or return to their own.
One common plot twist could be that they initially seem to be enemies but are actually long - lost brothers. Another might be that they both get caught in a strange alternate universe where their roles are completely reversed. And a third could be that an outside force tries to make them fight, but they end up teaming up against it.
Well, sometimes in these fanfictions, the reborn Ultron might find out that it was created with a hidden purpose by an even more shadowy figure. This discovery could lead it on a journey to uncover the truth about its origin, and along the way, it has to decide whether to continue its vendetta against the Avengers or not. It's really interesting to see how the writers play with this concept of self - discovery.
One of the most interesting plot twists could be the sharing of powers. For example, Naruto's ability to use chakra might combine with the unique demonic powers in Highschool DxD in unexpected ways. Maybe a character from Naruto's world gains a devil fruit - like ability from the Highschool DxD universe. Another could be a character from Highschool DxD learning how to use ninjutsu, which would completely change the power dynamics in their own world.
One of the most interesting plot twists could be when Harley realizes that Joker's love for her is just a part of his game. In many Suicide Squad interpretations, Harley is blindly in love with Joker. But if she discovers his true nature, it flips the whole dynamic. It makes her question her loyalty and could lead to her breaking free from his control and becoming a more independent character within the fanfic.
In certain fanfictions, a really interesting plot twist is when Harry Potter is sent back in time and ends up influencing Tom Riddle's early life in ways he didn't anticipate. This can lead to a completely different Hogwarts and wizarding world. For example, Harry might accidentally introduce a new form of magic that Tom then misuses. Or, there could be a plot twist where Tom Riddle's Horcruxes have an entirely different origin or purpose than in the original books, which throws Harry's understanding of how to defeat him into chaos.
It's likely Alucard. His vampiric powers are extremely potent. He can regenerate from almost any injury, has superhuman strength and speed, and can even manipulate shadows. In a crossover, he could potentially overpower many of the Devil May Cry characters, especially if he has the element of surprise.