In this fanfiction, it might be that Naruto is tricked into believing that his village has betrayed him. So, in his anger and despair, he decides to destroy everything related to it. He starts with the buildings and then moves on to any shinobi who tries to stop him.
Maybe Naruto gets some sort of dark power that makes him go berserk and start destroying everything in his path. For example, he could be influenced by an ancient evil curse.
It could be a new character that we haven't seen in the original Naruto series. This character might be jealous of Naruto's power and wants to see him destroy his own world so that he can take over the chaos that follows.
One possibility could be that Naruto is somehow transported to the world of Greek mythology where Olympus exists. Maybe his powerful jutsu are seen as a threat to the gods on Olympus. He could start by accidentally causing chaos in a nearby village which gets the attention of the minor gods. As they try to stop him, he realizes he has to fight back to protect himself and in the process, his attacks end up targeting Olympus.
In this kind of fanfiction, Naruto might be banished due to some false accusations or political conspiracies in Konoha. Once banished, he could decide to destroy Konoha out of anger and a sense of betrayal. He may have learned powerful jutsus during his exile and use them against the village that once rejected him.
Well, it could be that Naruto's newfound fear makes him hesitant in battles. He might struggle to use his usual jutsus because he's afraid of the potential consequences. For example, he could be afraid that his Rasengan might cause more destruction than intended and harm innocent people. So, in battles, he'd be constantly second - guessing himself, which would make for an interesting plot as his friends try to figure out what's wrong with him and help him overcome this fear.
In such a fanfiction, the plot could involve Naruto finally realizing the full extent of his past experiences. He might remember details about his parents that he had forgotten or repressed. For example, he could recall specific moments with his father, Minato, like how Minato taught him a certain jutsu in a dream - like memory. This newfound knowledge could make him stronger, as he'd have a deeper understanding of his heritage and the power within him.
It could also be that Naruto has been tricked. For instance, someone he trusts feeds him false information about the elemental nations being involved in a heinous conspiracy against him or his loved ones. This misinformation leads him to take drastic actions and start to destroy the elemental nations. Another idea is that Naruto loses control of his newfound and extremely powerful abilities. These abilities might be too much for him to handle and they end up causing destruction on a massive scale, starting with the elemental nations.
In the fanfic, Naruto might destroy the army in a very unique way. Instead of using his typical Rasengan or Shadow Clone Jutsu, he could discover a new power within himself. Maybe he unlocks a special form of Sage Mode that gives him the ability to control the elements in a completely different way, allowing him to take on the army with ease.
A possible plot might involve Naruto being exposed to some ancient and powerful knowledge or artifact. This discovery gives him the means to 'destroy' bloodlines in the sense that he can change the very nature of chakra within a person. He might use this new - found ability to break the cycle of bloodline - based power hierarchies. He could start with the major clans like the Uchiha and Hyuga, and as he spreads his influence, the concept of bloodline superiority slowly crumbles, leading to a new era in the Naruto world where a person's worth is determined by their own efforts and skills rather than their bloodline.
Well, perhaps Harry has finally had enough of the Ministry's corruption and inefficiency. So he decides to take it down using his powerful magic skills. He might start by exposing all the dark secrets hidden within the Ministry walls, which could lead to chaos and the downfall of those in power.
The plot might involve Percy gathering ancient artifacts or allies. He could go on a quest to find a weapon that can harm Gaea on a fundamental level. Along the way, he overcomes many challenges and personal demons. When he finally faces Gaea, he combines his strength, the power of his friends, and the magic of the artifacts to completely destroy her, bringing peace to the world of the gods and demigods.