There could be a group of rogue witches and wizards who are against the current system in the wizarding world. They oppose the Ministry of Magic's rules and see Harry Potter as a symbol of the establishment they want to overthrow, so they become the antagonists.
His friends like Ron and Hermione would surely be his allies. They have always been by his side in the original stories, so it's likely they'll be there in the fanfiction too, helping Harry in his fight.
It could be a new group of rogue ninjas who have a vendetta against Konoha. They might be led by a powerful and cunning ninja who has a personal grudge against Naruto or the village in general.
Another possibility is that an overzealous member of the Order who has gone too far in their methods of fighting Voldemort. Their extreme actions might make Harry think they have become as bad as the Death Eaters, so he starts to oppose them. For example, if this member starts using unethical spells on innocent people in the name of the greater good.
It's hard to say without more details about the fanfiction. But it could be some characters who benefit from Teddy not having rights, like power - hungry individuals or those with prejudiced views.
Maybe Harry Potter discovers a new dark threat in the fanfiction and has to fight it using his magical skills and the support of his friends. He could be facing a powerful dark wizard who has found a way to break through Hogwarts' defenses.
It could be a group of dark wizards who have a different ideology from Voldemort. They might not be interested in pure - blood supremacy but rather in power for power's sake. They could be more cunning and use more psychological warfare against Harry, which would force him to fight in new ways.
His friends from Hogwarts like Hermione and Ron would most likely support him. They have always been by his side through thick and thin in the original story, so in the fanfiction, they would continue to support Harry in his fight against the Ministry.
Hermione could help. She's very smart and could research about the dragon's weaknesses.
It could be a group of power - hungry humans who see the Laguz as a resource to be exploited. They might want to use the Laguz's unique abilities for their own gain, like using their strength in labor or their magical abilities for warfare.
In a dark corner of Hogwarts, Harry was fuming. Malfoy had once again taunted him about his parents. Harry's eyes blazed with anger. Without a second thought, he lunged at Malfoy, his wand at the ready. 'You won't get away with this anymore, Malfoy!' he shouted. Magic crackled in the air as they dueled, Harry's newfound determination pushing him forward.