In some fanfiction concepts, Naruto and Sakura might control the dead through powerful jutsu. Maybe they discover an ancient forbidden technique. For example, they could find a scroll that teaches them how to manipulate the souls of the dead. This could be a result of their continuous exploration and growth in the ninja world.
It could be the Akatsuki members. Since they are often the main villains in the Naruto universe, they might also play that role in this fanfiction. They could be trying to stop Naruto from using his control over Sakura to achieve something that would be a threat to their plans.
In some fanfiction concepts, it could be due to a new, powerful jutsu he discovers or perhaps as a result of some ancient curse or blessing that is bestowed upon him.
One consequence could be that it disturbs the balance of the ninja world. The dead are supposed to rest, and by controlling them, Naruto might be messing with the natural order. This could lead to other ninja clans or villages seeing him as a threat.
Perhaps in the fanfiction, Naruto controls Sakura in the sense that he influences her to see things from his perspective, like the importance of a certain mission or the true nature of an enemy. This could lead to them having a deeper bond and working more effectively together. He could use his charisma and leadership skills to bring out the best in Sakura.
In some fanfics, it could be due to a forbidden jutsu he discovers. Maybe he stumbles upon an ancient scroll that details the process of controlling the dead.
In fanfiction, if Harry Potter controls the dead, it could completely change the power dynamics in the wizarding world. It might give him an edge in battles, as he could summon the knowledge and skills of the deceased. For example, he could get strategic advice from great wizards of the past. However, it also raises moral questions. Is it right to use the dead in such a way? It goes against the natural order in the original Potter universe.
Well, obviously Sakura is one of the main characters. She is the one with the power to control dragons. And then there are the dragons themselves, which can be individual characters with different personalities. For example, there might be a wise old dragon that acts as a mentor to Sakura.
One consequence could be moral. They would have to deal with the ethics of controlling the dead. Are they disturbing the natural order? This could cause a rift between them and some of their friends and allies who might not agree with such a practice.
Foxes are quite common. Given Naruto's connection with the Nine - Tailed Fox, it makes sense that in fanfiction, he might be able to control other foxes. They can be used for scouting or as distractions in battles.