For a crossover with the My Hero Academia universe, Deku would be a good choice. He could learn a lot from the Sailor Scouts about using their powers for good and they could be inspired by his determination. They could also train together and combine their powers to take on stronger enemies.
One idea could be a crossover with the Harry Potter universe. Sailor Moon and her friends could attend Hogwarts and have to deal with both magical threats from the wizarding world and the dark forces they usually face. For example, they might help the students at Hogwarts fight off a new kind of dark magic that has similarities to the dark energy they combat in their own world.
The Sailor Scouts would probably be really curious about the Pokemon. Sailor Moon might befriend some cute Pokemon right away, like Pikachu. The Pokemon trainers, on the other hand, would be in awe of the Sailor Scouts' magical powers. They could learn from each other. For example, the trainers could teach the Scouts about Pokemon battles, and the Scouts could show the trainers some of their cool combat moves that don't involve Pokemon.
If we consider Akane, she could potentially have some interesting interactions with the Sailor Scouts too. She might envy their grace and power at first. But then she could learn from them and in turn, teach them about her own strength in martial arts. And for the villains in the Sailor Moon universe, they would see Ranma and his friends as either a threat or a potential tool to use in their evil plans. They might try to manipulate Ranma's curse or use his skills for their own gain.
The Sailor Guardians would likely be initially cautious around the Transformers. Sailor Venus might be the first to approach them, being the more outgoing one. She could try to communicate and find out their intentions. Optimus Prime, on the other hand, would probably be very diplomatic, trying to assure the Sailor Scouts that they mean no harm. The more impulsive Sailor Scouts like Sailor Jupiter might be a bit quicker to jump into action if she feels threatened, while the Autobots like Ratchet would be there to try and defuse the situation.
Sailor Moon would probably be really curious about Batman. She'd be constantly asking him questions about his gadgets and his mission. Batman, being the brooding type, might be a bit annoyed at first but would soon realize her good heart. He'd start to respect her powers and they'd form an unlikely alliance.
When it comes to Natsu and Sailor Mars, they could start off as rivals in terms of their fire - related powers. But as they train together and face challenges, they could develop a mutual respect. Natsu might learn some discipline from Sailor Mars' more refined use of her powers, and she could learn to be more spontaneous from Natsu. Their relationship could grow into a strong friendship, and they might even have a friendly competition to see who can defeat more enemies using their fire powers in a joint mission.
In this type of crossover, the characters' development would be a major part of the story. The Sailor Scouts, who are used to relying on their magic, might start to appreciate the importance of technology when they see the Power Rangers' advanced equipment. They could start to incorporate some of that into their fighting style. The Power Rangers could develop a deeper sense of friendship and loyalty, similar to what the Sailor Scouts have. They might also become more open - minded about different types of powers, as the Sailor Scouts' magic is very different from their own.
Ranma is hot - headed and impulsive. He would probably clash with Sailor Moon's more emotional and sometimes naive personality at first. But over time, they could learn from each other. Ranma could teach her to be more assertive in a fight, while she could teach him to be more in touch with his feelings.
Overall, Sailor Moon Crystal adheres closely to the manga. Some minor details might differ for the sake of animation or pacing, but the core elements remain the same.
I think it could be Naruto in his most powerful form, like when he has all the tailed beasts' chakra and is in his ultimate Sage Mode. His attacks are extremely destructive and he has a lot of combat experience. However, Sailor Saturn is also a very powerful character in the Sailor Moon universe. She has the power of destruction which is on a large scale. If they were to fight, it would be interesting to see how Naruto's positive energy and fighting skills would fare against Sailor Saturn's more passive yet extremely powerful destruction abilities. But overall, Naruto's versatility and his growth potential might make him the most powerful in a crossover scenario.