Definitely Geralt from The Witcher. His knowledge of monsters and magic could complement the Doom Slayer's brute force. They could work together to hunt down some powerful demons that are causing chaos in both their worlds.
One idea could be a crossover with the Halo universe. The Doom Slayer could team up with Master Chief to fight against a common alien threat that has invaded both their worlds. They could share their combat skills and weaponry knowledge.
One interesting aspect could be the contrast in their fighting styles. The Goblin Slayer is more methodical and strategic when dealing with goblins, using his knowledge of their habits. The Doom Slayer, on the other hand, is a force of pure destruction. In a crossover, perhaps they could learn from each other. The Goblin Slayer could pick up some of the Doom Slayer's more aggressive tactics, while the Doom Slayer might gain some strategic thinking from the Goblin Slayer.
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.
Well, one possible plot could be that Doom Slayer somehow gets transported to the Fairy Tail universe. He might initially be seen as a threat due to his intimidating appearance and his violent ways of dealing with enemies. But then, as the Fairy Tail members get to know him, they realize he's fighting against a greater evil. They could team up to take on a powerful dark wizard who has made a pact with demons similar to those Doom Slayer fights. The contrast between the magic - based world of Fairy Tail and the high - tech, gore - filled world of Doom would make for an interesting story.
There could be a cultural clash. The Doom Slayer comes from a more futuristic and hellish setting, while the Goblin Slayer is in a medieval - ish fantasy world. Their ways of communicating and understanding the world are different. However, this could also lead to some interesting exchanges. For example, the Goblin Slayer might be fascinated by the Doom Slayer's energy - based weapons, and the Doom Slayer could be intrigued by the magic and alchemy in the Goblin Slayer's world.
Good characterization is key. The Doom Slayer should stay true to his in - game persona - a silent, unstoppable force. For example, if he crosses over with a more talkative character from another franchise, the contrast should be well - written.
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.
Another interesting pairing would be Doom Slayer and Erza. Erza is a strong and disciplined mage. She would be intrigued by Doom Slayer's unwavering determination. They could bond over their shared sense of justice. Erza might even try to learn from Doom Slayer's single - minded focus on destroying evil. And Doom Slayer could be impressed by Erza's ability to handle various types of magic and her leadership within the Fairy Tail guild.