Yes, there are likely 'Bardock Kills Frieza' fanfics out there. The Dragon Ball universe has a huge fan base, and many fans like to create alternative storylines. You can try searching on fanfic websites like FanFiction.net or Archive of Our Own.
The plot could start with Bardock having a premonition of Frieza's future actions against the Saiyans even before the destruction of Planet Vegeta. He then secretly trains and discovers a new form or power that allows him to stand up to Frieza. When Frieza arrives to destroy the Saiyans, Bardock reveals his newfound strength and battles Frieza. After a long and intense fight, Bardock manages to defeat and kill Frieza, changing the course of the Dragon Ball universe. This could also lead to new alliances and power struggles among the remaining characters.
Well, it could be that in the fanfic, Bardock's group forms an unexpected alliance. Perhaps they team up with another powerful race or a group that has some sort of technology or magic that can counter Frieza. This alliance provides them with the means to not only fend off Frieza but also to ensure their survival. Another possibility is that there is some sort of time - travel or dimension - hopping involved. They could escape to a different time or dimension where Frieza can't reach them.
In a 'Bardock's group survive Frieza' fanfic, a major element is the alteration of the power balance. This can be achieved in multiple ways. For example, the fanfic might introduce a powerful artifact that boosts the Saiyans' power. The relationships within Bardock's group are also important. If they have strong bonds and are able to communicate effectively, they can better coordinate against Frieza. Moreover, the fanfic may explore different Saiyan cultural elements that give the group an edge. For instance, a long - forgotten Saiyan ritual or knowledge that helps them in their fight for survival.
At first, it might be tense. Bardock is a hardened Saiyan warrior from a different era, and Goku has grown up on Earth with a very different set of values. But as they start to communicate, they would find common ground in their Saiyan blood. Goku's pure - heartedness could gradually win over Bardock, and Bardock's strength and pride could earn Goku's respect.
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.
At first, it could be a bit rocky. Bardock is used to the harsh Saiyan ways, while Goku has been raised on Earth with different values. But as they spend time together, they start to understand and respect each other. Bardock could become a mentor to Goku, teaching him advanced Saiyan fighting techniques and Goku could teach Bardock about friendship and love.
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.
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.
In a 'Bardock meets Goku fanfiction', perhaps Bardock is pulled through time and space and lands on Earth during one of Goku's battles. Goku is shocked to see his father but quickly accepts him. Together, they team up against a powerful villain. Bardock shares his Saiyan knowledge with Goku, which helps Goku unlock new powers and defeat the enemy.