It's also likely that he's telling the story to himself, just reminiscing about his past. Raditz might be in a situation where he's alone and thinking about all the things he's been through, so he starts talking out loud as if he's telling a story to an invisible audience. He could be reflecting on his mistakes or his great moments during his life.
Perhaps he's telling the story to someone he wants to recruit. By telling an exciting story, he hopes to persuade the person to join his side or follow his lead. For instance, if there's a powerful being on Earth that Raditz thinks can be of use, he might tell a story to show his own strength and the potential benefits of teaming up with him.
He could be telling the story to his fellow Saiyans, if there are any around. Maybe he's sharing his knowledge or experiences with them.
If Raditz survived in fanfiction, he would likely have a complex relationship with Goku. He might start to see the value in Goku's way of life. Goku could try to reform him, and Raditz could slowly become a more positive force in the Dragon Ball Z universe.
It's possible that Raditz tells a story about his journey to Earth. He could start from when he first set off from his home planet, what he encountered during the long travel in space, and how he finally located Earth. He might also include his initial impressions of Earth, like the strange environment, the different power levels of the beings here compared to what he was used to on his home planet.
Perhaps the main antagonist could be a new character. This new character could be an ancient evil that has been awakened by the presence of the Saiyans on Earth. They see Bardock and Raditz as a threat to their plans of taking over the universe and thus try to eliminate them.
Sakura could be an ally. She might be curious about Naruto's new powers and help him control them. Also, Kakashi could be an important ally. He's always been there for Naruto, and he would likely try to understand and train Naruto with his new Saiyan abilities.
Piccolo might also be a savior. He has a soft spot for Gohan since they trained together. He could use his strategic mind and powerful attacks to outwit Raditz and rescue Gohan. Maybe he teams up with Goku for an even more epic rescue mission.
It's usually the author or the creator of the story. They have the control over this aspect.
Raditz could be redeemed by sacrificing himself for the greater good. For example, if there was a powerful enemy threatening the Earth and he steps in to take a fatal blow meant for someone else, like Gohan or Goku.
Perhaps she is telling the story to her younger siblings. They might be sitting around her, wide - eyed with excitement, as she weaves her tale.
It could be to the little children in Arendelle. Olaf loves making people happy, especially kids, so he might be sharing his story with them to bring some joy.
It could be the author. In many books, the author is the one who tells the story, guiding the readers through the plot, introducing characters, and creating the overall atmosphere.