One possible plot twist could be that Ragna discovers he is the cause of a major historical event that he previously thought was just a part of history. For example, he might find out that his actions in the past led to the rise or fall of a powerful kingdom.
Maybe Ragna goes back in time and meets a younger version of an enemy. However, instead of fighting, they become friends, which completely changes the future dynamic between them. This new friendship could lead to different alliances and power balances in the future he came from.
One interesting plot twist could be that Harry goes back in time and accidentally changes the sorting of some of the characters. For example, Draco Malfoy could end up in Gryffindor instead of Slytherin, which would completely change their relationship and how events unfold in the wizarding world.
One possible plot twist could be that Optimus discovers he is the cause of an event in the past that he was trying to prevent. For example, his presence might accidentally lead to the earlier awakening of a powerful enemy. Another could be that he meets a younger version of himself and has to convince his past self to trust him without revealing too much about the future.
One possible plot twist could be that when they go back in time, they accidentally change something that has a huge impact on their future relationships. For example, Naruto might unknowingly prevent Sasuke from leaving the village in the past, which could completely change how they interact in the present they return to. Another could be that they find out a hidden truth about their parents or the village's past that was covered up, like a secret alliance that their predecessors were involved in.
Well, perhaps a major plot twist is when Percy goes back in time and realizes that the events he thought were accidents in his own time were actually carefully orchestrated by a character from the past. This would add a whole new layer of mystery and conspiracy. Also, he might find that a prophecy he was trying to prevent in his time was actually meant to happen in the past for a greater good, which would be a huge turn for his mission.
One common plot twist could be that the female Naruto discovers she has a hidden power that was dormant in her original timeline but is awakened in the past. For example, she might find out she has a special connection to an ancient jutsu or a long - lost clan. Another plot twist could be that her actions in the past change the future in unexpected ways. Maybe she accidentally prevents the birth of one of her important friends in the original timeline. Or perhaps she gets caught up in a political intrigue that was not part of her original story and has to navigate through it carefully to ensure she can still return to her own time and that the future she knows is not completely altered.
His sense of purpose might also change. In his original time, he might have been fighting for a certain cause. But in the past, he could discover new things to fight for or new values to uphold. Maybe he realizes the importance of preserving certain aspects of the past that were lost in his future, and this changes his overall attitude and personality as he becomes more of a preserver than a fighter in some ways.
A really interesting plot twist could be that Steven goes back in time and discovers that the Diamonds had different motives than he originally thought. Maybe they were being influenced by some other force in the past, and by going back, he uncovers this mystery. Also, he could find out that some of the things he thought were his friends' ideas were actually planted by an outside source long ago. This would completely change his understanding of the relationships and history in the Steven Universe world.
One possible plot twist could be that Naruto discovers a hidden conspiracy within the Blood Prison. Maybe the prison is being used for something more sinister than just holding criminals. Another twist could be that Naruto's friends believe he's a traitor for ending up in such a place and he has to prove his innocence to them while still trapped in the prison.
Well, perhaps a plot twist could be that when Kirito goes back in time, he discovers that his own existence in the past was a key factor in creating the problems he faced in the future. So, he has to figure out a way to change things without erasing himself. Or, he could go back and find that the person he loves in his original timeline has a completely different personality or role in the past, which throws him off and makes his feelings really complicated.
Perhaps the writer goes back in time thinking they can use their knowledge of the future to their advantage, but instead they find that the past has its own rules and forces that prevent them from doing so. For instance, every time they try to introduce a future concept, it gets distorted or erased by some mysterious force, adding a sense of mystery and frustration to the story.