Who could be the main antagonists in 'harry goes back and raises himself fanfiction'?

One possible plot could be that Harry uses some powerful time - turning magic to go back in time. He then has to hide his true identity from his younger self while trying to guide and raise himself. Maybe he teaches his younger self some advanced magic that he didn't learn until later in his original life, like more complex Patronus charms or advanced defensive spells.

Perhaps Orochimaru, if he somehow discovers Ino's time - traveling. He has always been interested in power and forbidden jutsu. He might try to use Ino's ability for his own gain, and if she resists, he would become an antagonist. He could also try to stop her from changing things that he wants to keep as they are for his own evil purposes.

Team Rocket could still be antagonists. Even if Ash goes back in time, they might be up to their old tricks of trying to steal Pokémon. Only this time, Ash has the advantage of knowing their future plans and can thwart them more easily.

There might be an ancient evil entity that has been trapped within the university grounds for centuries. When Harry arrives, it senses his power and tries to use him to break free. This entity could manipulate other students and staff to achieve its goal, making it a very dangerous and complex antagonist.

The main antagonists could be those who don't want Harry to receive a proper Hogwarts education. Maybe some dark wizards who fear that Harry will become too powerful if he goes through the Hogwarts training. So, they plot to keep him away from Hogwarts.

Well, Garrosh Hellscream could be an antagonist in this fanfiction. Even if Anduin goes back in time, Garrosh's thirst for power and his extreme views could put him at odds with Anduin. Garrosh might see Anduin as a threat to his own plans for the Horde. The Nathrezim, those sly demons, could also be antagonists. They are masters of manipulation and could try to use Anduin's presence in the past to their own advantage. And don't forget about the various cults that serve the Old Gods. These groups would likely oppose Anduin as he tries to disrupt their plans to free their dark masters.

I think Dobby could be an important character. Since Harry is raising himself, Dobby might take it upon himself to secretly help Harry. He could provide some food and small comforts when Harry is all alone. Another character could be Hedwig. She would be more than just a pet; she could be Harry's only true companion, helping him in small ways like delivering messages or even warning him of danger.

Maybe some evil wizards or dark creatures. They could sense the power of the growing dragon and want to either control it for their own evil purposes or kill it to prevent it from becoming a threat to their plans. They would see Bilbo as an obstacle in their way.

One possible main antagonist could be the headmaster of the killer school. If the school is a place that values strength and ruthlessness, the headmaster might be a tyrant who enjoys seeing students struggle and fail. He or she could be constantly setting up dangerous situations for Harry just to test him.

Voldemort would still be a major antagonist. Even in the Marauders era, he was starting to rise to power. Also, the Death Eaters who were following him at that time could be antagonists. They would be causing trouble and trying to spread their pure - blood ideology.