Some of the pure - blood supremacist families who still hold grudges against Harry could be antagonists. They might not approve of Daphne getting involved with Harry, seeing him as a threat to their traditional values. For example, some of Daphne's extended family members who are still stuck in the old ways could try to break them up.
Some former Death Eaters who escaped justice could be the main antagonists. They might be plotting to bring back Voldemort's ideology in a more covert way. Another possibility could be new dark wizards who emerge, seeing the post - war chaos as an opportunity to gain power.
In the 'Harry loved Daphne after the war' fanfiction, it could start with Harry feeling lonely and disillusioned despite the victory. Daphne, on the other hand, is trying to find her place in the new wizarding society. By chance, they meet in Diagon Alley. Harry is immediately attracted to Daphne's beauty and grace. As they start talking, he discovers her kind heart and her unique views on magic and society. This leads to them spending more time together, and eventually, love blossoms between them.
The Malfoy family could be antagonists. They might see Harry as an enemy still and not want Daphne, a pure - blood, to marry a half - blood like Harry. They could try to create problems between the two, spreading rumors or trying to sabotage their relationship.
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 Dementors could be the main antagonists. They are always a threat in Azkaban, sucking out the souls and happiness of the prisoners. They would be constantly trying to get at Harry and Daphne.
It could be some rogue ninjas who were against the peace treaties after the war. They might form a group and try to disrupt the newly - established peace in the ninja world.
It could be some remaining monsters that survived the giant war and are now seeking revenge. They might target Nico specifically because of his role in the war. Another possibility is some rogue demigods who didn't like the outcome of the war and blame Nico for it.
The two of them could also interact with the Ministry of Magic officials. Harry, being a hero of the war, would have a certain influence. He might try to push for reforms in the Ministry, and Daphne could support him. They would have to deal with bureaucrats who may not be as eager for change, like some of the old - guard pure - bloods who still hold positions of power in the Ministry.
Another option for antagonists could be a new organization that rises in the power vacuum left after the war. They might have different ideologies from Naruino and his village. For example, they could believe in total domination rather than the peace and co - existence that Naruino stands for. They would see Naruino as a threat to their plans and try to eliminate him.
The antagonists could be a group of corrupted Ministry of Magic officials. They have turned to the dark side for power and are trying to rewrite the laws to suit their evil plans. Harry, being the hero, sings 'This is War' to expose their wrongdoings and fight against their tyranny.