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.
In a 'raven meets superman fanfiction', it could start with Raven sensing a strange energy signature which turns out to be Superman. She's intrigued and decides to observe him from afar. However, Superman notices her and mistakes her for a threat at first. But when they start to communicate, they realize they both have a lot to offer in terms of knowledge and power. They might then go on an adventure to stop an interdimensional threat that only their combined powers can handle.
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.
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.
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.
Obviously, Raven and the Sparda fan would be the main characters.
Lex Luthor would be a great villain. He could be plotting to destroy Superman once and for all while also trying to outsmart Batman. His intelligence and resources make him a formidable foe for both heroes.
It could be Trigon. Since Raven has a connection to him, he might see the baby as a way to get revenge on Raven or as a powerful tool for his evil plans. He could try to corrupt the baby's powers for his own use.
Obviously, Raven and the members of the Bat family like Batman, Robin (Damian), and maybe others like Alfred. Raven is the key character from the damirae side, and the Bat family members are central to their own side.
Darkseid could be the main villain. Imagine Darkseid learning of Superman's ability to time - travel and using it to his advantage. He could try to invade different time periods to gain more power and resources. Superman would have to fight him across time and space to protect all of existence.
It could be someone like Ra's al Ghul. He is a powerful and complex villain that both Batman and The Shadow would have a hard time dealing with. His global influence and long - life plans would pose a great threat to their efforts to protect Gotham and the world.