The Doom Slayer and a Greenskin Warboss. It would be a clash of brute strength. The Warboss would see the Doom Slayer as a worthy opponent and would try to prove his own might. The Doom Slayer would just be focused on destroying the Greenskin hordes, but their individual combat styles and the chaos that would ensue from their encounter would make for a great story.
The Doom Slayer and a Space Marine would be really interesting. They both are combat - focused and have a strong sense of duty. They could start off as rivals, each thinking their way of fighting is superior, but then come to respect each other after facing a common enemy like the forces of Chaos.
The Doom Slayer and Vali would make for an exciting interaction. Vali is a very powerful and ambitious character in High School DxD. He would likely see the Doom Slayer as a rival or a potential ally in his quest for power. The two of them could engage in some epic battles or team up against a common enemy. Additionally, the interaction between the Doom Slayer and Koneko would be interesting. Koneko is a quiet and strong - willed character, and she might be curious about the Slayer's motives and his unwavering dedication to his mission.
Definitely the Emperor of Mankind. The contrast between the all - seeing, all - powerful (sort of) Emperor and the single - minded, brutally efficient Doom Slayer would be fascinating. They could have a complex relationship, with the Emperor trying to direct the Slayer's rage for the 'greater good' of the Warhammer universe.
Blake could be a very interesting character in a RWBY Doom crossover fanfiction. Her ability to create illusions and her cat - like reflexes could give her an edge in the Doom universe. Also, her complex backstory and her more reserved nature compared to some of the other RWBY characters would make for an interesting dynamic when interacting with the Doom Slayer and the other denizens of the Doom world. She might be able to use her stealth to sneak up on demons or create illusions to distract them while the others attack from different angles.
Another interesting interaction could be between Vaggie and the Doomguy. Vaggie is protective of Charlie and the hotel's mission. When she meets Doomguy, she might be suspicious of his motives. She could be constantly on guard around him, and he might be a bit annoyed by her over - protectiveness. Their relationship could start off as very tense but could develop in interesting ways as they get to know each other better.
Definitely Joker and Makoto Yuki. Joker is the leader of the Phantom Thieves, very confident and strategic, while Makoto Yuki is a strong and silent type. Their leadership styles could clash or complement each other.
Definitely the interactions between the two versions of Leonardo. The 2012 Leo is more light - hearted in some ways compared to the very serious 2003 Leo. They could have some great moments of leadership clashes and then learning from each other. For example, the 2003 Leo could teach the 2012 Leo some of his more stoic leadership techniques.
I think the interaction between Joker (from Persona 5) and Yu (from Persona 4) would be really interesting. They are both leaders of their respective groups, so they could exchange leadership strategies and learn from each other. Also, Morgana and Teddie would be hilarious together. Morgana's serious yet sometimes clueless nature and Teddie's over - the - top and comical personality would create some great comedic moments.
The Doom Slayer and Ruby. Ruby is young and full of hope, always looking for adventure. The Doom Slayer is a stoic, battle - hardened warrior. Their interaction would be really interesting. Ruby could be in awe of his strength and weapons, and the Doom Slayer might see a bit of his own unwavering will in Ruby.
The Doom Slayer and Ruby would be an interesting pairing. Ruby is young and full of energy and hope, while the Doom Slayer is a silent, stoic force of destruction against evil. Their interactions could be really cool, like Ruby trying to understand the Doom Slayer's lack of words but seeing his determination and being inspired by it. And the Doom Slayer might see Ruby's potential and unwavering spirit in the face of danger as something similar to his own.
I think the combination of the Doom Slayer and Anya Oliwa from Wolfenstein could be really interesting. Anya is a strong and intelligent character. She could provide the Doom Slayer with valuable information about the Wolfenstein world, like the layout of Nazi bases and their technology. Meanwhile, the Doom Slayer could protect her with his incredible combat prowess. This dynamic could lead to a story where they work together to uncover a deeper conspiracy that links the demons and the Nazis.