One idea could be that the Doom Slayer is transported into the Warhammer universe. He might start by facing off against hordes of Orks in a brutal melee, using his signature weapons. His superhuman strength and unwavering determination would make him a force to be reckoned with among the various factions.
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.
One possibility in this fanfiction could be that Naruto's positive and determined nature clashes with Doctor Doom's tyrannical and power - hungry ways. Maybe Naruto is transported to Doctor Doom's world and tries to bring his sense of justice there. He might use his ninja skills to outwit Doom's high - tech defenses.
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.
Character development is key. If you're bringing in characters from different franchises, make sure they stay true to their original selves while also growing in the new environment. For instance, if Captain Kirk enters the 40k universe, he would be shocked by the brutality but also use his wits to survive. You also need to think about how the different powers and abilities will interact. In a crossover with Harry Potter, how would a Space Marine react to magic? There are so many possibilities to explore.
One great 'Warhammer 40000 Crossover Fanfiction' is the one where it crosses with Star Wars. It's really interesting to see the Imperial Guard facing off against Stormtroopers. The different combat styles and ideologies make for a great read.
A plot could involve the forces of Warhammer trying to harness the power of the Doom Slayer. They see his incredible combat abilities and want to use him in their battles. However, the Slayer has his own mission and is not easily swayed, leading to a conflict of interests and some intense battles.
There's 'Doom Patrol's Adventure in the Arrowverse'. This fanfiction takes the Doom Patrol and drops them into the Arrowverse. It's exciting as it allows for crossovers with characters like the Flash and Green Arrow. The Doom Patrol's surreal abilities and backstories add a whole new layer of complexity and fun to the Arrowverse.
One great Doom Slayer crossover fanfiction is the one where he crosses over with the Halo universe. It's exciting to see the Doom Slayer's brute force combined with the high - tech weaponry of Halo. The way the two different art styles and storylines blend is really engaging.
A good 'Good Doom Crossover Fanfiction' has well - integrated universes. For example, if it's a crossover with 'Metroid', the different technologies and atmospheres of both Doom and Metroid need to blend smoothly. The Doom Slayer's movements in the more enclosed and alien - like environments of Metroid should feel natural.