A powerful dark wizard or sorcerer could be the antagonist. He might be after the Saiyan's life - force or some special energy that Gohan and Bardock possess. This wizard could use dark magic to create all sorts of obstacles for them, like illusions, cursed landscapes, and powerful minions.
In the fanfiction, their relationship could start with distrust. Bardock might not trust Gohan because he is part human. However, as they face challenges together, like fighting off some common enemy, they start to understand each other. Gohan could show Bardock his unique fighting style which combines both Saiyan and human techniques. Bardock, in turn, could pass on his knowledge of Saiyan heritage and the importance of Saiyan pride. This would gradually strengthen their bond.
It could be a new villain created specifically for the fanfiction. Maybe a powerful sorcerer who wants to steal the Saiyan's power.
One possible interaction is that Bardock could spar with Goku and Gohan. He'd test their limits and see how much they've learned about fighting. Another could be Bardock sharing stories of Planet Vegeta with them, which would be really interesting for Goku and Gohan to hear.
In this fanfiction, it could start with Gohan exploring an ancient Saiyan relic. Unbeknownst to him, this relic has the ability to bring back the spirit of Bardock. Once Bardock appears, he is initially confused about where he is and who Gohan is. Gohan, being the kind - hearted person he is, explains the situation. As time passes, Bardock starts to train Gohan, pushing him to new limits. Gohan also shares his knowledge of Earth's culture and values with Bardock, which makes Bardock see a different side of life compared to the brutal Saiyan culture he knew. This interaction could change both of their perspectives and lead to a new understanding between the past and present of the Saiyan race.
In the 'Gohan meets Bardock' fanfiction, it might start with Gohan stumbling upon an ancient Saiyan relic that somehow connects him to Bardock. Bardock then appears as a spirit or through some time - traveling magic. They have a deep conversation about the purpose of the Saiyan race. Bardock could be proud of Gohan for breaking the mold of the typical Saiyan, being more about protecting the innocent rather than just fighting for power. Gohan, in turn, could be inspired by Bardock's raw Saiyan spirit and find a new way to combine it with his own values.
The main characters are bound to be Bardock and Gohan. Bardock with his fierce Saiyan warrior past and Gohan, who has his own unique blend of Saiyan and human qualities. There might also be other supporting characters like Piccolo who could pop in to add some more depth to the story, or perhaps even Bulma if she has some role to play in the time - travel or dimension - hopping aspect of the story.
Well, it could be that Gohan meets them in a strange time - space rift. Bardock and Gine, seeing Gohan, might be initially shocked at his different Saiyan - human hybrid form. Gohan could then tell them about the future, about the battles against the Saiyans' enemies. They might form an unlikely alliance to face some new threat that spans across different timelines.
In this fanfiction, Bardock might be shocked to see how much Goku has grown and the family he has built. He could be proud of Goku for becoming such a strong and kind - hearted Saiyan. And when he meets Gohan, he might see the potential in him as well, maybe even offer some unique Saiyan training tips that are different from what Goku has taught Gohan.
It could be someone who doesn't want Gohan and Zeno to form an alliance. Maybe a rogue god from another universe who fears that if Gohan influences Zeno, his own plans for universal domination will be thwarted.
Well, it could be about Bardock somehow traveling through time to meet Gohan. Maybe Bardock wants to see the potential of his future grandson's power and they end up training together for a bit.