Perhaps Harry travels back to his own childhood and tries to change how he was treated by the Dursleys. He could also try to influence his younger self to be more confident and prepared for the challenges ahead at Hogwarts.
One interesting plotline could be Harry going back in time to prevent certain deaths, like Sirius Black's. He might use his knowledge of future events to change the course of history and save his loved ones.
One interesting plotline could be Snape going back in time and trying to prevent the death of Lily Potter. He might use his knowledge of the future to change certain events that led to her demise. Another could be him attempting to correct his own past mistakes, like his relationship with James Potter. Maybe he goes back and tries to befriend James earlier to avoid all the enmity that grew between them over the years.
In some fanfictions, Naruto might go back in time and try to save his parents. He could alter the events that led to their deaths. This would not only change his own life but also have a huge impact on the entire ninja world as his parents were very powerful ninja.
One interesting plot could be Harry going back in time to prevent the death of his parents. He might use his knowledge of future events to outwit Voldemort before he becomes too powerful. Another could be Harry traveling back to his first year at Hogwarts and changing how he interacted with certain characters like Snape, which could lead to a different dynamic between them throughout the series.
Another plotline could be Albus Severus trying to correct a mistake made by one of his ancestors. This might involve him interfering with a family feud or an old magical spell gone wrong. As he travels through time, he has to be careful not to disrupt the fabric of time too much, which adds an element of danger and suspense to the story.
One possible plotline could be that Harry and Severus go back in time to prevent certain tragedies from happening in the wizarding world. For example, they might try to stop Voldemort's rise to power much earlier. Another could be that they go back to change their own relationship. Maybe in the original timeline they were enemies, but now they have a chance to become allies or even friends.
One interesting plotline could be Harry using his future knowledge to prevent certain tragedies. For example, he might stop the death of his parents earlier, which would completely change the course of the wizarding world. He could also use his knowledge of dark magic threats to better prepare the wizarding community, like warning about Voldemort's rise much earlier.
Well, in some 'Harry Potter goes back in time' fanfics, Harry might go back to his first year at Hogwarts. He could then use his more advanced magical skills (from his future experiences) to solve the mystery of the Philosopher's Stone in a completely different way. This might involve him befriending different people earlier or even changing the course of how the challenges in the dungeon were set up.
One interesting plotline could be that in the alternate universe (au), Harry Potter discovers a world where magic is used in completely different ways. For example, instead of using wands, they use amulets. Another could be that he finds himself in a world where Voldemort won the war in his own universe, and he has to figure out how to change things in this au. Or perhaps he travels to an au where Hogwarts is a school for all magical creatures, not just witches and wizards.
One interesting plotline could be Harry trying to prevent the death of his parents. He might use his knowledge from the future to change certain events. For example, he could try to stop Voldemort's rise to power earlier in the Marauders' time.
Well, in some 'Harry Potter travels the multiverse fanfiction', there could be a plotline where Harry discovers a universe where he was never born. This would force him to re - evaluate his own importance and the role he plays in the grand scheme of things. Maybe he has to figure out how to bring magic back to that universe or deal with the consequences of his non - existence. Another cool plotline might be that he travels to a universe where the wizarding world is at war with a race of powerful magical creatures he's never encountered before, and he has to broker peace.