There could be a new dark wizard or witch emerging. This character could be jealous of Harry and Hermione's influence and see the baby as a way to get to them. They might try to harm the baby or turn it against Harry and Hermione, creating a lot of conflict and danger in the story.
One possible antagonist could be a dark wizard who wants the baby for its own dark purposes. Maybe the baby has a unique power that the dark wizard wants to harness. Also, there could be some jealous wizards or witches in the community who are envious of the Golden Trio's fame and don't want to see them succeed in this new family venture. They might spread rumors or try to create problems for the Trio and the baby.
In this fanfiction, the plot could start with Harry and Hermione realizing that they want to start a family together in a non - traditional way. They find a baby who has some special powers or a mysterious background. As they adopt the baby, they have to figure out how to raise it while also juggling their own lives as important figures in the wizarding world. They may need to seek help from their friends like Ron and Ginny to create a stable and loving environment for the baby.
The Ministry of Magic itself could be an antagonist. If they don't approve of Hermione's adoption due to her age or some bureaucratic reasons, they could try to take the baby away. They might think she's not fit to raise a child, which would create a lot of conflict in the story.
Voldemort's remaining followers could be antagonists. They might see the baby as a new threat or a potential weapon. They could try to kidnap the baby to use its power for their own dark purposes.
In this fanfic, the social workers who are overly strict or have some biases could be antagonists. If they don't approve of Cheryl's lifestyle or think she has some flaws that make her an unfit adoptive mother, they could create a lot of obstacles for her in the adoption process. This would add drama to the story as Cheryl tries to prove herself worthy of adopting the baby girl.
A new dark wizard could emerge in the wizarding world. This wizard might be jealous of Harry's fame and power and think that by getting to Lily, he can gain some sort of advantage. He could try to steal Lily's magic or use her to spread fear in the wizarding community.
In the 'Harry and Daphne baby fanfiction', it could be a new dark wizard who rises to power. This wizard might believe that the baby has some sort of power that could stop him from achieving his goals. So, he makes it his mission to eliminate the baby. Also, there could be some magical creatures that are being controlled by a dark force and are sent to attack Harry, Daphne and their baby because they sense the baby's potential power.
The adopted child could be a muggle - born with a great potential for magic. Maybe their parents were killed by dark wizards who were against muggles in the wizarding world. Harry and Hermione, having both experienced prejudice, would be determined to give this child a chance.
Voldemort could be an antagonist if he somehow returns and sees the baby as a threat or a symbol of a new hope that he wants to destroy. He might target the baby to get back at Harry and Tom.
Well, perhaps in the fanfiction, Harry and Hermione find a child who has special needs in terms of magic. For example, the child has an uncontrollable magical power that scares other families away. But Harry and Hermione see the potential in the child. They start to work together, with Hermione using her vast knowledge of magic and Harry using his own experiences, to help the child learn to control their power. As they do this, they form a very close family unit.