He might change the course of some major battles. For example, he could prevent the destruction of certain planets that were destroyed in the original timeline.
In some fanfiction ideas, when Vegito goes back in time, his power could be affected by the different energy levels in the past. Maybe the ki in the past is purer, which could either enhance his power further or require him to adapt in a new way. Also, if he has to hide his true power to not disrupt the timeline too much, he might have to find new ways to use his skills subtly.
She could meet her younger self. This would be an interesting encounter as she could offer advice and guidance to her younger version. Maybe she could help her younger self to be less afraid of her powers.
He could change the course of major events. For example, he might prevent the rise of a powerful villain. This would have a huge impact on the entire galaxy. Maybe he could save some characters who died in the original timeline.
One interesting aspect could be that Luke goes back to a time when the Sith were just emerging. He could try to root out the Sith threat before it became as powerful as it did. He might have to be very careful not to disrupt the timeline too much, but his Jedi wisdom could be a great asset in this time - traveling adventure.
In this fanfiction, Sora might change key events. Maybe he could prevent some of the tragedies that occurred in the original story. For example, he could save a character who was lost before.
One possible plot could be that Kagome goes back in time and tries to change a major event in the past. For example, she might try to prevent a big battle that had a lot of casualties. She could use her modern knowledge and skills to her advantage in the past, like using first - aid knowledge to save lives.
She might change important events in the wizarding world. For example, she could prevent certain dark magic incidents or save characters who died in the original timeline.
Well, one possibility could be that Kurama goes back to a time when he was first captured by the shinobi. He might try to change things so that he doesn't end up in their hands initially. He could use his knowledge of the future to outwit his captors and escape much earlier, and perhaps even start a new life in a different part of the world.
Well, he might meet his ancestors. It could be really interesting to see how they interact and what kind of influence he has on their lives. Maybe he'll change some small events that end up having a big impact on his present time.