One potential character could be Goku from Dragon Ball. Goku's love for fighting strong opponents and his Saiyan nature would make for an interesting dynamic with BlackWarGreymon. Another could be Naruto from Naruto. Naruto's ability to see the good in others might clash or connect with BlackWarGreymon's more complex personality.
In a crossover fanfic, characters like Batman could be paired with BlackWarGreymon. Batman's strategic mind and detective skills would be interesting when dealing with BlackWarGreymon. He might try to figure out BlackWarGreymon's motives and weaknesses. Another character could be Sailor Moon. Her positive energy and power of love could have an impact on BlackWarGreymon, either changing him or causing him to react in a unique way.
Well, characters like Superman could be paired with BlackWarGreymon. Superman's superhuman strength and moral code would contrast with BlackWarGreymon's more morally ambiguous nature. Also, characters from the Final Fantasy series, such as Cloud Strife. Cloud's cool and brooding personality and his sword - fighting skills could lead to some epic battles or unexpected alliances with BlackWarGreymon in a crossover fanfic.
Percy Jackson and Carter Kane would be a great pair. Percy is used to the Greek mythological world and its challenges, while Carter has a deep understanding of Egyptian magic and mythology. Their different perspectives could lead to some interesting teamwork, like when they face a monster that has aspects of both Greek and Egyptian mythology, such as a Sphinx with the ability to use water attacks like a Greek hydra.
Captain America might be paired with Ultron as well. Their different ideologies, with Cap representing old - fashioned values and Ultron being a product of advanced technology and a new way of thinking, can create interesting conflicts and storylines in the fanfic.
Jackie Estacado from 'the darkness' is an obvious choice. His connection to the Darkness power makes him a central figure and his skills and personality can drive the story forward in a crossover.
Well, if we consider other shonen - style series, someone like Naruto from 'Naruto' could be a potential crossover character. His ninja skills and strong will could create some interesting dynamics with the 'world trigger' characters.
One interesting concept could be the interaction between BlackWarGreymon and characters from different universes. For example, how he would react to meeting characters with very different moral compasses or powers. Another concept might be his journey in a new world created by the crossover, facing new challenges and making new alliances or enemies.
Lucario is also a popular choice to be paired with Pikachu in crossovers. Lucario has its own unique abilities related to sensing and combat. When combined with Pikachu's electric attacks, they can form a formidable team. The contrast between Lucario's more serious and stoic nature and Pikachu's cute and energetic personality also adds depth to the story.
Batman is a very popular character to pair with Superman in crossover fanfics. Their dynamic is well - known in the DC universe, with Batman being more of a dark and brooding detective while Superman is the all - powerful alien. Their different personalities and methods of crime - fighting make for great story material.
Well, Ben is the central figure. But don't forget about Kevin Levin. His ability to absorb and use different forms of energy could be very relevant in the Warhammer universe filled with all kinds of strange energies. In Warhammer, a Chaos Sorcerer could be a main character. The way his dark magic would interact with Ben's powers and the overall plot would be full of potential. Also, Rook Blonko from Ben 10 could be important. His skills and loyalty could add a different dynamic to the story as they explore the Warhammer universe together with Ben.
In terms of anime characters, Ichigo Kurosaki from 'Bleach' could be an interesting addition. His ability to see and fight spirits could be related to Kiva's battles with Fangires. They could end up in each other's worlds and have to learn to use their powers together to fight off both Hollows and Fangires.
Another possibility is Kamen Rider Decade. Decade has the ability to transform into different Kamen Riders, and his presence in a crossover with Kickhopper could bring a lot of different elements into the story. He could use his powers to help Kickhopper access new forms or abilities, or they could travel through different Kamen Rider worlds together to stop a multiverse - level threat.