One possible villain could be Bizarro. Bizarro is always causing chaos and with Superboy and Superman together, it would be an interesting fight. Bizarro's reversed logic and powers would make it a tough battle for them.
In a 'superboy meets superman fanfiction', there could be an epic battle at first as they test each other's powers. Maybe Superboy is initially a bit rebellious and wants to prove himself against Superman. Then they could end up teaming up to fight a common enemy like Lex Luthor or some other powerful villain from the Superman universe.
One aspect to consider is the character development. Superboy might learn valuable lessons about humanity, love, and family values from the Kents. It could also be a story of acceptance, where the Kents welcome Superboy into their family despite his differences. For example, they could help him control his powers better or understand the human world more deeply.
Lex Luthor would be a great choice. He's Superman's long - time nemesis. He could form an alliance with some of Batman's foes like the Joker. Luthor could use his intelligence and resources to create a plan that only Superman and Batman together could stop.
Trigon, Raven's father, could also be the main villain. He might see Superman as a new obstacle in his path to spreading chaos and destruction. His demonic powers would be a huge challenge for both Raven, who has a complex relationship with him, and Superman, who has never faced such a dark and powerful entity from another dimension.
Lex Luthor could be a likely main villain. He hates Superman and would see Damian as a tool to use against him. He might manipulate Damian into believing Superman is a threat to Gotham, causing Damian to attack Superman first.
They also interact with the rest of the Young Justice team differently. Superman is seen as this big - time hero, while Superboy is more of the up - and - coming, rough - around - the - edges type. In some fanfics, Superboy's relationship with the team helps him grow into his own hero, separate from Superman's influence.
In Young Justice fanfiction, Superman and Superboy often have complex relationships. Superboy might struggle with living in Superman's shadow. He could be constantly trying to prove himself as a worthy hero, not just a clone. For example, in some stories, Superboy takes on dangerous missions alone to show he's as capable as Superman.
Some fanfictions explore the idea of a power struggle between them. Even though Superman is more experienced, Superboy might have some unique powers or a different way of thinking. This can lead to some interesting conflicts and how they resolve them, while still maintaining their bond as heroes in the DC universe.
The plot could be Superboy discovers Krypto while on a routine patrol. Krypto's super - dog abilities might help Superboy in a fight against a new villain in town.
Another theme is the relationship building. Since Lois has a pre - existing relationship with Superman, the fanfictions often explore how she forms a new connection with Superboy. It could be a friendship, a mentorship or even a romantic interest in some cases. For example, in some stories, Lois sees Superboy as a younger version of Superman she can guide, while in others, there's a spark of something more between them.