The plot could involve the Doom Slayer being mistaken for a powerful devil in the Chainsaw Man world. As he tries to find a way back to his own dimension, he has to deal with various devil hunters who see him as a threat. Meanwhile, a powerful devil emerges that is interested in the Doom Slayer's power. Denji, realizing the Doom Slayer is not an enemy, decides to help him fight this new devil.
One possible plot could be that the Doom Slayer gets transported to the Chainsaw Man universe. He teams up with Denji to fight against a new type of demon that is a combination of the demons from Chainsaw Man's world and the hellish creatures from the Doom universe. Their combined strength and different fighting styles make for an epic battle.
One possible plot could be that the Doom Slayer somehow gets transported to the world of Goblin Slayer. He then uses his advanced weaponry and combat skills to help the Goblin Slayer in his never - ending fight against the goblins. Maybe they team up to take on a super - powerful goblin boss that neither could defeat alone.
However, Denji as Chainsaw Man also has his own set of powers. He can transform into a powerful chainsaw - like being and has shown great resilience. But compared to the Doom Slayer, he lacks the same level of experience in dealing with the kinds of threats that the Doom Slayer has faced on a regular basis. So, overall, the Doom Slayer would probably be more powerful in a direct comparison.
One possible plot could be that the Doom Slayer somehow gets teleported to the Hazbin Hotel universe. He then has to deal with the demons there, which are different from the ones he usually fights. The hotel staff might initially be afraid of him, but then realize he could be an asset in dealing with more malevolent demons.
Well, the plot could involve a rift opening between the two worlds. Goblins start pouring into the Doom world and the Doomguy has to deal with them. Meanwhile, the Goblin Slayer follows the goblins through the rift and they end up working together to close the rift and stop the chaos. They might exchange combat techniques and learn from each other's experiences along the way.
In a 'doom slayer in another world fanfiction', perhaps the Doom Slayer is transported to a post - apocalyptic world different from his own. Here, he has to adapt his fighting style to new threats. He could discover new ways to upgrade his weapons using the resources of this strange world. Maybe he even has to face a new kind of demon that has evolved in this different environment.
Well, one idea for the plot of such a crossover fanfiction could be that the Doom Slayer gets transported to the world of Wolfenstein. He then has to figure out how to deal with the different type of enemies there, the Nazis. Meanwhile, the Wolfenstein hero could be intrigued by the Doom Slayer's advanced weaponry and otherworldly strength. They might start off as cautious allies, but as they face more and more challenges together, they form a strong bond and a united front against the combined evils of demons and Nazis.
One possible plot could be that the Doom Slayer is somehow transported to the world of Goblin Slayer. He then teams up with Goblin Slayer to take on an especially powerful horde of goblins that have been corrupted by demonic forces from Doom. Their combined skills in combat, the Doom Slayer's superhuman strength and arsenal, and Goblin Slayer's knowledge of goblin tactics would make for an epic battle.
The character development would be fascinating. Naruto, who is used to fighting in the world of ninjas, would have to adapt to the extremely violent and demon - filled world of Doom. His moral compass might be tested in new ways as he faces the pure evil of the demons. He could also bring some of his values from the Naruto universe, like friendship and loyalty, to the Doom universe and influence the way he fights and interacts with the environment.
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.
The fanfiction might also play with the idea of redemption for the female demon. Since the Doom Slayer is often associated with justice, perhaps he sees some potential in her to change. It could be a story of her trying to break free from her demonic nature with the help of the Doom Slayer. Their relationship could develop from pure enmity to something more complex, like an unlikely alliance or even a romantic connection in a more extreme take on the story.