If Darth Vader travels to a time when he was still Anakin Skywalker, he might have a chance to redeem himself earlier. Seeing his younger self could make him realize the mistakes he made and try to change the path that led to his dark transformation. His character could become more complex as he battles with his past self's idealism and his current self's dark nature.
Darth Vader traveling forward in time could expose him to new forms of governance and social structures. This might make him question the autocratic rule of the Empire. He could start to develop a more empathetic side as he sees the consequences of the Empire's actions on different planets and species. His character would then shift from being a pure tool of the dark side to someone with a more nuanced view of power.
Naruto's character would experience a significant transformation. He'd be exposed to a whole new level of power and control in Vader's world. His development could go in different directions. He could either become more like Vader, ruthless and power - hungry, which would be a huge deviation from his original self. Or he could use the knowledge he gains to become a stronger defender of what he believes in. He might also learn to be more strategic and less impulsive, as the Star Wars universe demands a different kind of thinking compared to the ninja world he comes from. His relationships would also change, as he'd have to interact with different species and characters in the Star Wars setting, and these new relationships would shape his character further.
Perhaps it would start off rocky. His grandchildren would be wary of him because of his reputation. But as they get to know him, they realize he has changed and they start to form a bond. They might learn from his experiences and he from their fresh perspectives on life. It could be a relationship of mutual growth.
The story might start with Harry being somehow transported to Vader's universe. He'd be shocked by the new environment, but his quick thinking would help him adapt. Then he'd cross paths with Vader, and the adventure would begin.
If Darth Vader travels back in time to the Clone Wars, his presence could cause a lot of chaos. He might try to take control of the Sith plans from Dooku. This would change the power dynamics within the Sith and also how they interact with the Separatists. It could also mean that Anakin Skywalker's journey to the dark side might be different. Maybe he would be influenced by Vader in a different way, either being pushed further into the dark side more quickly or being pulled back from it if Vader has some sort of change of heart during his time travel.
Their relationship could become more understanding. As they travel through time and see different events together, Luke would gain a deeper understanding of what led his father to become Darth Vader. Vader, in turn, might see Luke's unwavering hope and goodness more clearly, which could soften his stance.
Darth Vader would likely be conflicted. On one hand, he could see the potential in his younger self to become a powerful Sith. On the other hand, he might be reminded of his own lost innocence. He might give his younger self some warnings about the path he is about to take, but also encourage the dark journey.
He might be shocked by the advanced technology. The Empire's weaponry would seem primitive compared to future tech. He could also be intrigued by the new forms of the Force if they had evolved.
If trained by Darth Vader, Naruto and Hinata's relationship could change in many ways. The shared experience of Vader's intense training would bond them. Naruto might see Hinata in a new light as she adapts to Vader's methods. Hinata could also grow more confident around Naruto. However, there could also be some tension as they both strive to meet Vader's high standards and compete for his approval, but overall, it could lead to a more mature and interdependent relationship.
His presence could change the power balance. If he sides with the Jedi, the Sith would be at a disadvantage. The Sith rely on secrecy and manipulation, but with Darth Vader knowing their plans, they would be exposed more easily.
Ezra's reaction would also depend on his state of mind at the time. If he was feeling confident and strong in the Force, he might be more bold in his approach to Vader. He could try to engage in a battle of wills through the Force, trying to push back against Vader's dark side influence. But if he was already weakened or doubting himself, the sight of Vader could make him feel hopeless and desperate, leading to a more erratic or panicked reaction.