One idea could be Dante from Devil May Cry being summoned to the world of Devilman by Akira. Akira could seek Dante's help to fight against a new type of devil that is beyond his capabilities. Dante, with his arsenal of weapons and devil - slaying skills, would then team up with Akira in his devilman form to take on this new threat.
Another plot could involve Vergil from Devil May Cry. He could end up in the Devilman universe and mistake Devilman for a regular devil at first. As he tries to slay Devilman, he realizes that there is more to him than meets the eye. This could lead to a complex relationship where Vergil has to decide whether to help Devilman in his fight against the greater evil in the Devilman world or continue on his own path of power - seeking.
Perhaps in the crossover, there could be a mix - up of powers. For example, the demons in the Devilman world start to gain some of the abilities that the devils in Devil May Cry have, like the ability to open portals or manipulate time in a small way. This would force Devilman and Dante to figure out how to counter these new and unexpected powers while also dealing with their own personal demons, both literally and figuratively.
One idea could be that Devilman and Devil Lady team up to fight a common enemy that is threatening both their worlds. Maybe a powerful demon from another dimension is trying to take over, and they have to combine their powers to stop it.
One idea could be that Pennywise from 'it' somehow enters the world of 'Devil May Cry'. Dante could mistake Pennywise for a particularly grotesque demon and engage in a battle. Pennywise, with his shape - shifting abilities, would constantly change forms to try and deceive Dante. Another plot could involve the characters from 'Devil May Cry' being lured into Derry by Pennywise's illusions. They then have to fight their way out while also dealing with the psychological warfare that Pennywise is known for.
A plot could revolve around a new enemy that threatens both the world of How to Train Your Dragon (where Toothless is from) and the Devil May Cry universe. The characters from both universes have to team up. For example, Vergil might be initially skeptical of Toothless but then come to respect his power. Toothless could also interact with the different weapons and magic in the DMC world in an interesting way.
One idea could be a crossover with Neon Genesis Evangelion. Devilman and the Eva pilots could team up to fight a common enemy that threatens both their worlds. Maybe a new type of demon that has the ability to control Angels.
A crossover with the Castlevania universe would also be cool. Dante could find himself in Dracula's castle, facing off against classic Castlevania monsters while also dealing with his own demonic foes. It would be interesting to see how he interacts with the Belmonts.
A possible plot is a magical artifact from Fairy Tail's world that is sought after by demons in Devil May Cry's universe. The Fairy Tail gang teams up with the Devil May Cry crew to protect it. The artifact might have the power to either destroy all magic or enhance it to uncontrollable levels. Dante and Natsu could have a friendly rivalry over who is stronger and who gets to fight the main villain. Another plot idea is that some of the Devil May Cry characters are sent back in time to the Fairy Tail world's past. They have to adapt to the magic - based society and help the Fairy Tail founders with a great threat that was once thought to be long forgotten.
One idea could be that Dante from Devil May Cry is somehow transported to the Marvel universe. He teams up with the Avengers, like Iron Man. Dante's unique combat style and devil - slaying abilities would be a great addition to the team. For example, he could use his Rebellion sword against powerful foes that the Avengers are having trouble with, such as Loki if he were to return in a more powerful form.
One idea could be that Naruto somehow ends up in the Devil May Cry world. He might mistake some of the demons there as similar to the tailed beasts he knows. For example, he could try to 'befriend' a demon in the DMC world thinking it's like how he dealt with Kurama. Another idea is Dante teaching Naruto some swordsmanship. Dante's flashy and powerful combat style could blend well with Naruto's own energetic fighting moves.
One idea could be a crossover with the Bayonetta series. Dante and Bayonetta could team up to fight a common, powerful demon. Their different fighting styles would make for some epic battles and interesting interactions. For example, Dante's flashy swordplay combined with Bayonetta's acrobatic and magical combat.
It's hard to say for sure, but Dante has a lot of experience and a wide array of powerful weapons and abilities. He has his Rebellion sword, Ebony and Ivory guns, and his devil trigger form which gives him enhanced strength, speed, and durability. However, Devilman also has his own unique powers, being part - human and part - devil. His ability to blend in with humans while having devil - like strength could give him an edge in certain situations.