In a kratos vs naruto fanfic battle, Naruto might have a chance if he uses his strategic thinking. He could use his shadow clones to surround Kratos and then attack from all sides. But Kratos is no pushover. His experience in combat is vast. He has fought against opponents with all kinds of powers. If he manages to break through Naruto's clones and get to the real Naruto, it could be over. However, Naruto also has his sage mode which gives him enhanced strength and perception. So it's a very tough call.
One idea could be a battle in a neutral dimension. Kratos, with his brute strength and god - slaying weapons, faces Naruto's ninjutsu and his ability to summon powerful creatures. Another idea is that they are forced to team up against a common enemy that threatens both their worlds. They start off clashing due to their different fighting styles and beliefs but gradually learn to work together.
If Naruto were Kratos' son in a fanfiction, the story could go in many directions. Naruto might have a different view on power. Instead of seeking recognition like he did in the original story, he could be more focused on using his power to right wrongs in a more forceful way. His relationships would also change. For example, his bond with Sasuke could be more of a rivalry based on power, similar to how Kratos has his own rivalries. And his training would be a combination of ninja training and whatever training Kratos would give his son, which might involve more physical and mental endurance challenges.
One possible storyline could be that Goku is accidentally transported to Alucard's world. They start off as enemies but then gradually learn about each other's powers and come to respect one another. Another could be that a powerful villain manipulates them into fighting each other. In this case, they might realize they are being used and team up against the real enemy.
It's really hard to say. Goku is extremely powerful with his Super Saiyan forms and incredible combat skills. But Alucard has his vampiric powers like immortality and the ability to control shadows. In a fanfic, it could go either way depending on how the author wants to write it. Maybe if the author wants to emphasize speed, Goku might have an edge. But if it's about dark, mysterious powers, Alucard could come out on top.
His powers would be much more physically dominant. He might not rely so much on ninjutsu but more on brute strength like Kratos. He could have the ability to rip his enemies apart instead of using shadow clones.
There could be a storyline where Issei challenges Goku to a friendly sparring match to test his own limits. As they fight, they exchange techniques and learn from each other. This could lead to Issei unlocking new forms of his own power, inspired by Goku's Super Saiyan forms. And Goku could also gain new insights into combat from Issei's more unorthodox fighting style.
It depends on the rules set in the fan - fiction. If it's a battle based on strategy, Issei might have a chance. He has shown to be quite cunning in his battles. But if it's a pure power - based fight, Goku has the upper hand. His years of training under various masters and his Saiyan heritage give him an edge. Also, Goku has experience fighting opponents much stronger than himself and finding ways to overcome them.
Well, it could be that Goku somehow ends up in the Naruto universe and has a son with a female character there. And this son has both the powers of a Saiyan like super strength and the ability to use chakra for jutsus. Maybe he's an outcast at first because of his strange powers but then becomes a hero.