Maybe an alien race that doesn't approve of Superman marrying a human. They could send an agent to Earth to try and stop the marriage. This agent could have powers similar to Superman's and create a lot of trouble for the couple, both in their personal lives and in their superhero duties.
A new character could be created as the main antagonist. For example, a mad scientist who was once rejected by Lois Lane. He decides to take revenge on her by targeting her relationship with Superman. He could create some dangerous technology that only Superman can stop, but at a cost to his relationship with Lois.
Obviously, Lois Lane and Superman are the main characters. Lois is a strong - willed journalist who is always in pursuit of a good story. Superman, on the other hand, is the powerful alien with superhuman abilities who has sworn to protect the Earth.
One possible plot could be the challenges they face in their daily lives while keeping Superman's identity a secret even within their marriage. For example, Lois might have to deal with the media constantly speculating about Superman's personal life and she has to be careful not to let any hints slip.
A really interesting plot could be that an alternate - universe version of Superman comes to their world. This causes some confusion for Lois as she has to figure out which Superman is the one she truly loves. Meanwhile, the two Supermen have to work together to fight a threat that endangers both their universes and their relationship.
Well, it's hard to say who the 'best' is as it depends on personal taste. But some popular authors include those who really capture the essence of the characters. For example, some authors who are good at writing the emotional side of Superman and Lois Lane's relationship. They can make you feel the love, the tension, and the drama between them.
Their relationship can be shown as even more loving and protective. Superman would be constantly worried about Lois and the baby, and Lois would appreciate his care while also being her strong - willed self. For instance, he might fly her to her doctor's appointments super - fast to avoid traffic.
One great fanfiction in this vein could be 'The Kryptonian Heir'. It beautifully explores how Superman deals with the impending fatherhood while still protecting Metropolis. It delves into his relationship with Lois during her pregnancy, showing their love and the challenges they face together.
Lex Luthor would be a great antagonist. He could see Superboy as a threat to his plans in Metropolis and try to find ways to discredit him or even eliminate him. Since Lois is a journalist, she might start to investigate Lex's actions against Superboy, which would put her in danger as well.
One interesting story could be about Superman taking Lois Lane on a flight around the world to show her the beauty of different places from a unique perspective. In this fanfiction, Lois might be initially scared but then filled with wonder as they soar over mountains and oceans.
Superman could rescue her. He'd use his super - hearing to locate her and his super - strength to break into wherever Lex is keeping her.
Lex Luthor would be a classic choice. He could be jealous of the protagonist who is reborn as Superman and see him as a threat to his own power and influence. Luthor might try to use his intellect to create new weapons or strategies to defeat Superman.