It's a continuation or alternate version of the Dragon Ball Z series, often featuring new characters and storylines. But beware, it's not an official manga.
Well, in these fanfics, Bulma might be an important character. She could use her intelligence to create some sort of device or plan to stop Evil Goku. Also, Piccolo would be there. His strategic mind and powerful attacks would be crucial in the fight. And of course, there might be new characters created specifically for the fanfic, like a mysterious sage who knows the secrets to defeating Evil Goku.
Well, Dragon Ball AF comics often feature unique character developments and expanded universes. They may incorporate elements not seen in the original series to keep things fresh and exciting for fans. Also, the art style could differ, giving a new look to the familiar characters.
One interesting plot could be Evil Goku's origin. Maybe he's a result of some dark magic or an alternate dimension's influence. Another plot might involve his battles against the regular Z - fighters. He could have new and more devious fighting techniques.
Honestly, I don't have a clear idea. It might be a role related to organizing events or overseeing certain aspects of the Dragon Ball AF storyline. But without more context, it's all just speculation.
Another way is that Goku could use the Spirit Bomb. He could gather energy from all living things on Earth and nearby planets. Android 21, being an artificial being, might not be able to withstand the pure energy of the Spirit Bomb. However, she could try to absorb the energy, but if Goku can overload her absorption capabilities, it would be his victory.
In a fanfiction scenario, Goku and Android 21's fight could attract the attention of other Z - fighters. Vegeta, for example, might be reluctant to help Goku at first but then realizes the danger Android 21 poses to the entire planet. Goku could also try to reach out to Android 21's good side, as he has a history of trying to redeem his enemies. This could add an interesting moral dilemma to the story, whether to fight or try to save her.