Goku is one of the strongest characters in the manga universe. He has insane strength, speed, and energy projection abilities. His determination and training have made him a force to be reckoned with.
Goku's strength in the manga is off the charts! He can defeat powerful enemies with his various techniques and transformations. His power level keeps increasing through intense training and battles.
Highlight their shared experiences. They both have been through a lot with the Saiyan threats and other villains. Writers can recall those moments and show how they supported each other during those times. Also, their shared love for Gohan can be a great way to strengthen their bond. They both want the best for their son and can work together towards that goal.
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.
The story could start with Goku being pushed to his limits by Goku Black's attacks. But then, he remembers his training with the Kai's and how they taught him to focus his energy in a more efficient way. He then uses this knowledge to create a more powerful Kamehameha that breaks through Goku Black's defenses and kills him.
If Goku Black fuses with Goku in fanfiction, the story would progress in a complex way. The fused form might go on a journey to understand itself. Since it has two very different personalities combined, it would face a lot of internal conflict. This could be used to explore themes like identity and the struggle between good and evil. Externally, the fused Goku could attract new enemies who see it as a threat to their power or plans.
As the story progresses, some fanfictions might explore a begrudging respect. Despite their differences, they recognize each other's power and fighting abilities. For example, they could have a series of battles where they start to understand each other's strategies better.