If Goku time travels, his powers could change in several ways. For example, if he travels to a time when the power levels were generally lower, like the early days of the Saiyans, his current power might seem overwhelming. He could easily defeat foes that were once considered strong. However, if he travels to a future where new threats have emerged, his powers might be relatively weaker compared to the local powerhouses. He would then have to train harder and adapt to the new power scale.
In a time - travel scenario for Goku, his powers would face a lot of changes. Imagine he travels to a time when the Saiyans were still under the control of the Tuffles. His Super Saiyan powers would be a shock to them. He could use his Super Saiyan form to quickly gain an upper hand in any conflicts. But if he travels to a time where the concept of Ki was not fully understood, like the early days of Earth's martial arts, he would have to start from scratch in terms of teaching others about Ki. His own power development might also be stunted as he tries to adapt to the lack of understanding of Ki in that time. Also, if he travels to a future where there are new forms of energy manipulation, he might need to abandon his old ways of using Ki and learn new techniques.
Well, Goku's powers in a time - travel situation are quite interesting. Let's say he travels back in time to a point before he learned the Kaio - ken technique. He could introduce this technique to his past self earlier, which would change the course of battles he had in the past. But if he travels to a time with different energy sources, like a time when the Namekian Dragon Balls were first created, his Ki control and power might be affected. He might have to learn to harness the unique energy of that time. And if he travels to a future with advanced technology that can enhance power, like power - amplifying suits, he could use those to boost his already formidable strength.
His relationship with Vegeta would also change. If Goku goes back to a time when they first met, he could try to befriend Vegeta right away instead of being enemies first. This would change the entire dynamic of their rivalry. They might become allies much sooner and train together, which would lead to both of them becoming even stronger at an earlier stage.
Well, his relationship with Vegeta would be interesting. If Goku went back in time and showed Vegeta the SSJ God form too early, Vegeta might become more competitive or even jealous earlier. He might push himself even harder to catch up, which could lead to more intense rivalries and also more joint training sessions between them.
If Goku travels back in time, his relationship with Bulma could be very different. In the past, she was more of a guide to him. But if he goes back with his current knowledge and power, he could become more of a protector for her. He might also be able to prevent some of the dangerous situations she got into in the original story.
One idea could be Goku traveling back to the Saiyan - Planet Vegeta days. He could try to prevent the destruction of the planet by Frieza. Maybe he'd train with his father Bardock and change the power dynamics among the Saiyans. Another plot could be Goku going to the future to meet his descendants and see how they've carried on the Saiyan legacy. He could also time travel to key moments in his own battles, like going back to his fight with Vegeta on Earth and using his future knowledge to end the fight more quickly.
Their relationship could become more of a teacher - student dynamic. Goku could teach Android 18 about the ways of the Saiyans and their fighting techniques from different eras during the time travel. Android 18, in turn, could show Goku some of her android - specific skills and how to use them more effectively. This exchange of knowledge could bring them closer and make them a more formidable team.
One interesting plot could be Goku traveling back in time to train with his younger self. He could teach his younger version some new techniques, like the Instant Transmission at an earlier stage. This would change the power dynamics in the earlier story arcs and lead to different battles against foes like Vegeta. Maybe the Z - Fighters would be stronger and better prepared for future threats.
His relationship with Obi - Wan would also change. If Anakin travels to a time when he was just a young Padawan again, Obi - Wan might see a different side of him. Anakin could use his future knowledge to become a better student, and Obi - Wan would be proud of him. Or, if Anakin travels to a time before he met Obi - Wan, he could approach their relationship from a new perspective when they do eventually meet.
Goku's godlike power might make his time travel more precise. Normal time travel in the Dragon Ball universe can be a bit haphazard, but with his godly energy, he could target specific moments more accurately. For instance, he could arrive at the exact second he wants to in the past or future.
In this fanfiction, they might have an epic sparring session. Adult Goku could teach Kid Goku some new techniques, like the Instant Transmission. It would be amazing to see how Kid Goku reacts to Goku's Super Saiyan forms.
In fanfiction, a female Goku can also change the relationships. The male - dominated friendships and rivalries in Dragon Ball Z could be shaken up. Her presence could make the male characters act differently. For example, Krillin might be more protective of her, or Gohan could look up to her in a different way. This can create new and interesting sub - plots within the story.