Often, in 'Goku Harem Fanfic', Goku becomes more aware of his romantic side. He might be a bit more in tune with the emotions of the female characters around him compared to his original portrayal in the Dragon Ball series, where he was mostly focused on fighting and training.
In such fanfictions, Goku might develop by becoming more of a mentor to Gohan. He could teach Gohan new fighting moves and also how to control his emotions better during battles.
In other fanfictions, they could be rivals. Goku is always looking for a strong opponent, and Sailor Moon's unique powers could make her an interesting rival. They might have battles where they test each other's limits, but also learn to respect each other in the process. They both have strong beliefs in protecting their worlds and those they love, so even as rivals, they could end up on the same side when a greater threat emerges.
In some lemon fanfiction, their interaction can be filled with tension. Goku, being the good - natured Saiyan, may be initially wary of Frieza. But as the story progresses, they might find common ground. For example, they could start to respect each other's power.
Writers often start by changing Goku's personality traits. Instead of his usual kind - hearted and naive self, they make him more cunning and self - centered. For example, they might have him using his powers for personal gain rather than to protect others.
The reaction among fans would be quite mixed. Some die - hard fans of the original series would be appalled as they have a clear image of ChiChi and Goku's relationship. They would see this type of fanfiction as a perversion of the original concept. On the other hand, there are those who are more open - minded and might see it as an interesting, if not controversial, exploration of the characters. But overall, the negative reactions would probably outweigh the positive ones.
Typically, the development of relationships in Goku x Harem fanfics is quite complex. Goku, being rather naive in the matters of love in the original series, has to learn about emotions and relationships. The female characters in the harem usually bring out different sides of Goku. Some might be strong - willed and challenge him, which helps him grow not just as a fighter but also as a person in terms of emotional intelligence. They often go through various trials together, like facing powerful enemies or solving intergalactic mysteries, which deepens their relationships.
They also develop their characters through their relationships. Goku has a unique relationship with Goten as his father. Writers might show Goku being a bit more laid - back as a dad compared to how he was with Gohan. Goten, in turn, might be shown as eager to please his father and live up to the family name. Additionally, in battle situations, their different fighting styles can further develop their characters. Goku's more experienced and instinctive style, while Goten is still learning and may be more impulsive.
Goku could escape by overpowering Broly. He might tap into his Super Saiyan forms, like going into Super Saiyan Blue or even Ultra Instinct if he's pushed far enough. His sheer power and fighting skills could allow him to break free from whatever restraints Broly has put on him.
It could be insanely powerful. Goku already has incredible power levels, and Goku Black is no slouch either. When they fuse, it's like combining two nuclear reactors. Their power could be so great that they could effortlessly destroy planets just by flexing their newfound power. They might be able to reach Super Saiyan forms that are far beyond what we've seen in the official series, with power levels that are basically off the scale.