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.
Well, it really depends on how the fanfiction is written. If the writer decides to give Percy some new powers or boost his existing ones, he could stand a chance against Kratos. However, Kratos is a force to be reckoned with. He's faced the most terrifying foes in his own universe. Percy is used to fighting monsters in the world of Greek mythology, but Kratos has fought gods on their own turf. So generally, Kratos has more of an advantage.
One interesting plot twist could be that Percy discovers a way to nullify Kratos' god - given powers. Maybe he finds an ancient artifact during the fight that has the ability to do so. Another could be that Kratos, instead of seeing Percy as an enemy, realizes they have a common goal against a greater evil in the fanfiction world and they end up teaming up.
It can start with mutual distrust. Doomguy is used to killing demons, and the female demon is afraid of him. But when they are forced into a situation where they have to rely on each other to survive, like being trapped in a small area surrounded by more powerful demons, they start to see each other in a new light. They begin to communicate, first out of necessity, and then gradually become more open with each other.
The Doomguy was once a marine. He was sent to Mars to investigate some strange happenings on a Union Aerospace Corporation (UAC) facility. The UAC had been messing around with teleportation technology and had accidentally opened portals to Hell. Doomguy found himself in the middle of a demonic invasion. His initial experiences on Mars were filled with fighting off hordes of demons, and this was just the start of his journey to become the ultimate demon - slayer.
Their interaction would be tense at first. Young Kratos, full of energy and unbridled aggression, might see old Kratos as a threat or an obstacle. Old Kratos, on the other hand, would be more reserved and cautious. But as they start to communicate, they would find common ground in their shared past and their connection to their family.
There's a fanfic called 'Doomguy in the Hidden Leaf'. In this one, Doomguy gets transported to the Naruto universe. It's interesting to see how he interacts with the different ninja clans, especially when his no - nonsense attitude clashes with the more traditional ways of the Leaf Village. It's a short but engaging read.