Perhaps Harry uses his time - control to age himself up or down at will. He ages himself up to gain more knowledge and wisdom quickly, and then uses that knowledge to outwit his enemies. Or he ages himself down to relive some of his childhood memories more vividly and find hidden clues about his destiny that he missed the first time.
Another plot might involve Harry exploring different timelines. He could find a timeline where Voldemort never existed and see how the wizarding world developed without the Dark Lord. This would give him insights into the true nature of good and evil and how much Voldemort really influenced the world.
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.
One popular plot is the redemption of werewolves. In these fanfictions, Harry Potter or other characters use their control methods to help werewolves integrate into wizarding society. For example, they might find a way to control the werewolf transformation so that werewolves can lead normal lives and not be shunned.
Well, Harry Potter himself is surely one of the main characters as the title implies he has the power to control time. Hermione Granger is likely to be another main character. She is always by Harry's side in the original series and would be there to help him understand and manage his new time - controlling ability, perhaps with her vast knowledge and logical thinking.
Well, in some fanfictions, Harry might control the Dursleys by making them understand the wizarding world. He could show them magical things and, as a result, they start to respect him and his abilities. This could lead to a whole new dynamic in the household, where the Dursleys are no longer mean but rather in awe of Harry and his magic.
One interesting concept could be how Harry's control over darkness is manifested. Maybe he can use it to cloak himself in shadows, like a new form of invisibility. Another could be that the darkness he controls has a sentient aspect and he has to negotiate with it.
A possible plotline is that Harry accidentally discovers the time - controlling power while exploring an old, forgotten part of the Hogwarts library. He then has to figure out how to use it without disrupting the fabric of time too much.
One interesting plot could be that Harry and Hermione travel back in time to change a major event at Hogwarts, like preventing the opening of the Chamber of Secrets. They might use their knowledge from the future to outwit Tom Riddle before he becomes Voldemort.
In some fanfictions, Harry goes back in time and decides to train himself better. He could seek out different magical knowledge or combat skills that he didn't have the first time around, which then changes his future interactions and battles. For example, he might learn ancient spells that give him an edge against Voldemort.
Another plot might involve Voldemort traveling to the future to see the destruction he causes. This could lead to a moment of self - reflection for him. He might realize the futility of his actions and perhaps change his ways. It would be a fascinating exploration of his character.
One interesting plot could be that they use the Time Turner to prevent a major disaster at Hogwarts that was overlooked in the original story. For example, they might stop a dark wizard from infiltrating the school during an important event.