The destruction of Marineford by Naruto would have far - reaching consequences. Politically, the World Government would be in chaos. They would likely try to hunt down Naruto with all their might. Socially, the people who once relied on Marineford for protection would be in a state of panic. And in terms of the overall story, it could lead to new alliances forming, like some pirates might team up with Naruto to fight against the remaining Marines, or some Marines might defect to try and stop the chaos Naruto has caused.
One consequence would be a major shift in the power balance in the One Piece world. The Marines would be severely weakened, and pirates might become more bold. Another consequence could be that Naruto would become a huge target for both the remaining Marines and other powerful forces in the One Piece world.
In the fanfiction, if Naruto destroys Marineford, it would disrupt the existing order completely. Economically, the trade routes that were protected by Marineford might be in jeopardy, leading to shortages and price hikes in various regions. Culturally, the Marines were seen as a symbol of justice in the One Piece world, and their destruction would shatter that perception. This could lead to a moral crisis among the people, and also, it would open the door for new ideologies to emerge as different groups try to fill the power vacuum left by the Marines.
Emotionally, Naruto himself might have to deal with the guilt of destroying Neji. Even if it was in the heat of battle, he might later realize that he took a life or seriously injured a fellow comrade. This could lead to internal struggles for Naruto. He might question his own power and whether he's using it in the right way. His relationships with other characters could also become strained as they try to come to terms with what Naruto has done.
If Naruto arrives at Marineford, it would be a chaotic and interesting scenario. Naruto's powerful jutsu like Rasengan and his ability to summon toads could change the balance of power. He might try to stop the fighting between the pirates and the marines, seeing the senseless destruction. His sense of justice and never - give - up attitude could inspire some of the characters there.
Naruto would be very curious. He'd want to understand what's going on. Once he figures out that there's a big battle between different factions, he'd try to find a peaceful solution. He might start by talking to the leaders, using his charm and persuasion skills. If that doesn't work, he'd use his ninja powers to protect the innocent. He's not one to just stand by when there's injustice.
The wizarding economy would be in chaos. Gringotts is the central bank of the wizarding world. Its destruction would mean that people's savings, vaults, and all the financial transactions would be disrupted. Wizards and witches would lose their trust in the financial system.
It might lead to a rift between Hogwarts and the other schools involved in the tournament. They could see Harry's actions as an act of aggression or a way of cheating, since the Goblet is such an important part of the event. However, if Harry can prove that the Goblet was corrupted or dangerous, they might come around. In the fanfiction, this could lead to a whole new set of diplomatic relations between the wizarding schools that need to be explored and resolved.
It's hard to say for sure, but Naruto himself could be a very powerful contender. His vast array of jutsu and his ability to harness the Nine - Tails' power would make him extremely formidable. He could easily take on many opponents at Marineford with his shadow clones and powerful attacks like the Tailed Beast Bomb.
One idea could be that Naruto characters are somehow transported to the Marineford world. For example, Naruto with his powerful jutsu might get involved in the battles at Marineford. He could use his Rasengan against the powerful foes there. Another idea is that the Devil Fruits in the Marineford world have an interesting interaction with the chakra system in Naruto. Maybe a character from Naruto eats a Devil Fruit and gains new and unexpected powers.
The consequences would be disastrous. Xenomorphs are extremely aggressive and dangerous creatures. They would likely start attacking the people in Naruto's world. Villages would be in chaos as they try to fend off these alien threats. Naruto would probably feel a great sense of guilt for creating such a menace.
The most immediate consequence would be the reaction from Naruto's friends. Sasuke, for example, would likely go on a quest for revenge. He has a deep bond with Naruto and would not let his death go unpunished. Sakura would also be devastated and might lose faith in the idea of peace between the villages.
The Akatsuki would surely be affected. They would lose one of their members, which could disrupt their plans. Also, it might change the way other characters view Naruto. Some might see him as a more formidable threat, while others might see him as a hero for taking out a dangerous enemy.