Kakashi would be intrigued. He'd probably study Naruto more closely to see how this new influence affects his growth as a ninja. He might also try to find ways to help Naruto blend Kratos - inspired skills with his existing ninja abilities. Kakashi would be open - minded about it, knowing that new sources of inspiration can lead to great power.
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.
Percy's reaction would be a mix of confusion and fascination. The world of Kratos is so foreign to him, with different rules and a much darker tone. However, he would also be drawn to the hero's journey that Kratos undertakes in the fanfiction, comparing it to his own journey as a demigod.
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.
In certain comic arcs, Heimdall tragically meets his end. The circumstances and reasons for his death can vary depending on the specific comic series and plot.
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.