It could also be a new dark wizard or witch who has emerged. This character sees Harry's memory loss as an opportunity to gain power. They might try to frame Harry for things he doesn't remember doing, causing chaos in the wizarding world and turning people against Harry so they can step in and take control.
Perhaps a corrupt Ministry official. They could see Harry's memory loss as a chance to cover up their own misdeeds or gain more power within the Ministry. They might try to manipulate Harry into signing documents or making statements that he wouldn't if he had his full memory, all in the name of furthering their own self - serving agendas.
It could be a new dark wizard who is jealous of Harry Potter's fame and success. This dark wizard targets Harry's child, thinking that by causing trouble for the child, they can somehow diminish Harry's reputation in the wizarding world. He might try to frame the child for various dark magic incidents around Hogwarts.
Borrowing power is a Chinese idiom that means to use or rely on some kind of power or situation to promote one's own or others 'development. This idiom is usually used in business, politics, or sports to express one's competitiveness and influence by taking advantage of the external environment. For example, a businessman might use the growth of market demand to expand his business, an athlete might use the support of the national team to increase his popularity and influence.
The main antagonist could be a powerful necromancer who combines the dark arts of Skyrim with some elements of Voldemort - like magic. He could be raising an army of the undead and causing chaos across Skyrim, which Harry has to stop.
It could be a new dark wizard who has a vendetta against Harry. This wizard might use a spell to stop Harry from eating, thinking it will weaken him before a final showdown. He could be someone who was once a follower of Voldemort and now wants to take his place and prove himself by getting rid of Harry.
Maybe an ancient evil spirit that was once bound but is now trying to break free by using the summoner as a conduit. This spirit could be manipulating events from the shadows, causing chaos in the wizarding world to draw the summoner out.
Perhaps it's a dark spirit that has been trapped in the Acrobleno for centuries. When Harry arrives, it senses his power and wants to possess him or use his magic for its own evil purposes. So it becomes the main antagonist, constantly trying to harm Harry and stop him from leaving.
It could be a jealous wizard who feels that Harry and his sister are getting too much attention in the wizarding world. This wizard might try to undermine their achievements and even put them in danger.
It could be Mr. Weasley. Since he's the head of the family, he might be the one driving the idea of taking the Potter fortune to better provide for his large family. He has the authority within the family and might think he's doing what's best in a tough situation.
Perhaps an ancient spirit that has been awakened by the imbalance in the life - death cycle due to Harry becoming the Master of Death. This spirit sees Harry as the cause of the chaos and tries to destroy him to restore the balance in a way that is harmful to the wizarding world.
In an alternate dimension, the main antagonist could be a dark entity that has emerged from the very fabric of the dementions themselves. This entity could be using the Dementors as its minions, controlling them to do its bidding. It would be a powerful and mysterious foe, and Harry would have to discover its true nature and weaknesses in order to defeat it.