The fanfiction could start with Harry being magically transported to Kaguya's world. He'd be confused at first but quickly realize he has to fight to survive. Harry's wand would be his main weapon. He might learn some new spells during the fight, perhaps a spell that can nullify Kaguya's ability to freeze time. As the fight progresses, both characters would start to respect each other's power, leading to an unexpected alliance at the end.
Well, Harry is a very determined and resourceful wizard. He has overcome many powerful enemies in his own world. But Kaguya is on a whole different level of power. She has the power to create dimensions and manipulate time. Harry would need to be extremely clever and use his magic in ways he's never done before. For example, he could combine different spells to create a super - spell. But even then, Kaguya's raw power might be too much for him to handle. So, in most cases, Kaguya would likely win, but with Harry's unpredictability, there's always a small chance he could pull off a victory.
In this fanfiction scenario, Naruto could potentially use new and untested jutsu. He might draw on the power of his nine - tailed fox in a completely different way. Maybe he'd combine Sage Mode with some secret Uzumaki clan technique he discovers during the fight.
Perhaps in this fanfiction, the court in the wizarding world has been corrupted. Harry discovers some dark secrets within the court system. He then decides to fight against it to bring justice. He might start by gathering evidence against those who are misusing their power in the court.
Well, perhaps Teddy is in some sort of danger. Maybe he's being targeted by dark wizards because of his connection to Harry. Harry, being the heroic type, decides to fight to protect Teddy. He could use his magic skills and the support of his friends like Hermione and Ron to keep Teddy safe.
Well, it could be that Harry is facing some new dark forces in the fanfiction. Maybe he discovers a hidden group of dark wizards who are plotting against Hogwarts, and he decides to fight back to protect his school and friends.
In a 'Harry Fights Alone' fanfiction, the plot could involve Harry being betrayed by his friends. Maybe they are put under a spell that makes them turn against him. Harry then has to face the dark forces all by himself. He might have to rely on his own wits and the few spells he has mastered alone. For example, he could be in a situation where he has to battle Voldemort's minions without Ron and Hermione to back him up, and he discovers new powers within himself during this struggle.
Well, perhaps Kaguya would use her otherworldly powers to protect Harry from Voldemort. Maybe she'd teach him some unique magic that's different from the wizarding world in Harry Potter. For example, she could introduce him to some ancient spells from her own realm.
In a Harry Potter vs Odin fanfiction, it could start with Odin thinking Harry is a threat to the Asgardian way. Harry, on the other hand, is just trying to protect Hogwarts. The fight might involve Odin using his powerful spear Gungnir while Harry combines his Patronus charm with some of the more powerful dark arts spells he's learned in his fight against Voldemort. But Harry would be reluctant to fully embrace the dark arts as it goes against his nature.
Well, perhaps Harry has to use his magic skills to resist some sort of spell or curse that is trying to force him into hibernation. Maybe there are dark forces at work trying to put him out of action for a long time.
Maybe Harry Potter discovers a new dark threat in the fanfiction and has to fight it using his magical skills and the support of his friends. He could be facing a powerful dark wizard who has found a way to break through Hogwarts' defenses.