There could be a power - hungry being who wants to use Goku's mother for their own gain. When Goku tries to meet her, this being tries to stop him because they know that if Goku and his mother reunite, they will be able to oppose their evil plans together.
Goku's reaction could be a mix of shock and happiness. On one hand, he never expected to actually meet his parents. On the other hand, he has always longed for a family connection. He might start asking them a million questions right away about their lives, Saiyan culture, and what it was like when he was born.
Loki would also be a difficult adversary. He's very cunning and could use his tricks and illusions to try and outwit Goku. Goku would need to rely on his senses and ki to see through Loki's deceptions.
Vegeta could be a great rival. He might see Goku's new position as God of Destruction as another thing Goku has achieved that he hasn't. This could fuel their competitive nature even more.
In general, it's a bit of a toss-up. The strength of Manga Goku and Anime Goku can vary depending on the specific arcs and battles. Sometimes, it might seem like one is stronger in a particular situation, but that could change in another.
Well, Vegeta would be a likely character. He might be initially suspicious of the female Goku. Maybe he thinks she's a threat or just can't believe there's another Goku - like being. He could be there to add some comical moments as he tries to understand the situation.
Chi - Chi might be one of the first to support them. Despite her past relationship with Goku, she could see how happy Goku is with Android 18 and decides to be happy for them. Also, Krillin would likely support the marriage. He has a deep friendship with both Goku and Android 18. He knows Android 18 well and trusts Goku, so he would be all for their union.
It could be a female Namekian. Since Namekians are also very strong and have their own unique culture, a female Namekian could catch Goku's eye. They might bond over their mutual respect for life and their experiences with fighting powerful foes.
Well, it could be that Goku meets his mother in a dream world. Maybe she gives him some advice on how to become even stronger. She might share some long - forgotten family secrets with him too.
Another possible main character could be the villain that forces the two Gokus to meet. This villain could be a new, super - powerful threat that the two Gokus need to deal with. Their meeting becomes a crucial part of the story to defeat this powerful foe.