It could be someone from Goku's past who has a vendetta against him and takes advantage of the chaos during the Cell Games. For instance, an old enemy who was thought to be defeated but managed to come back stronger and wants to finish Goku off while he's weakened from the fight with Cell.
One common theme is the clash of ideologies. Goku is all about protecting the innocent and having a fair fight, while Cell is more about self - preservation and domination at first.
Perhaps a rogue Saiyan from another part of the universe. This Saiyan has heard about the Super Saiyan powers on Earth and wants to prove his superiority. He shows up at the Cell Games and challenges Goku and Gohan. He has a different fighting style, more brutal and less honorable than the Saiyans on Earth. His presence adds a new layer of conflict as Goku and Gohan have to decide whether to fight him on his terms or uphold their own values.
It's really hard to say. Goku has his amazing fighting abilities and power-ups. But the Avengers have a lot of different powers and strategies. If the fight takes place in the Marvel Universe, the Avengers might have some home - field advantage. However, Goku's adaptability and his ability to quickly learn in battle could give him the upper hand. Maybe it would end in a draw if both sides respect each other's power and stop the fight before it goes too far.
In a 'Goku vs Avengers' fanfiction, Goku's extreme power levels would be a major factor. His Super Saiyan forms could potentially overpower many of the Avengers. However, the Avengers have their own unique skills and teamwork. Iron Man could use his high - tech suits to analyze Goku and try to find weaknesses. Captain America would lead the team in terms of strategy. But Goku's speed and strength might be too much for them to handle in the end.
One possible storyline could be that Goku is accidentally transported to Alucard's world. They start off as enemies but then gradually learn about each other's powers and come to respect one another. Another could be that a powerful villain manipulates them into fighting each other. In this case, they might realize they are being used and team up against the real enemy.
It's really hard to say. Goku is extremely powerful with his Super Saiyan forms and incredible combat skills. But Alucard has his vampiric powers like immortality and the ability to control shadows. In a fanfic, it could go either way depending on how the author wants to write it. Maybe if the author wants to emphasize speed, Goku might have an edge. But if it's about dark, mysterious powers, Alucard could come out on top.
One possible interesting plot could be Gohan unlocking a new, unexpected power level during the Cell Games. For example, instead of just going Super Saiyan 2, he could access a form that combines the power of both Goku and his own latent abilities. This new form could have unique characteristics like different colored ki blasts or enhanced speed and strength that not only surprises Cell but also gives Gohan a whole new perspective on his power.