It could be Loki. Since he has a knack for causing trouble, he might find a way to cross over to the wizarding world. He could manipulate the dark wizards and use their magic for his own devious plans. Maybe he wants to steal the Philosopher's Stone to gain immortality and use it to take over Asgard as well.
A powerful dark wizard who has somehow managed to tap into Asgardian magic could be the main antagonist. He might have found an ancient artifact that gives him access to Thor's powers but twists them into something dark. He wants to rule both the wizarding world and Asgard, and sees Harry and Thor as the biggest threats to his plans.
Perhaps a new character, a hybrid of a dark wizard and a Frost Giant. This being could be created by a dark ritual that combines the cold magic of the Frost Giants with the dark arts of the wizarding world. He would be after the power of both Thor and Harry, aiming to create a new realm where he is the sole ruler, using the powers of both Asgard and the wizarding world to his advantage.
Chapter 644, "Has Shang Shaojing Actually Gone Bankrupt?!", is the clearest early answer because it turns Actually Gone Bankrupt's situation into a concrete plot event. The chapter gives readers a real answer by opening on Su Yinwan was already on her way home when she saw the trending...
Look to Chapter 25 for the clearest answer. It begins with Therefore, from his childhood, Jiang Shixu had felt an extreme aversion to..., keeps building through Over time, he naturally developed a gap of estrangement between himself..., and lands on Having worked beside Shen Lan for over a decade.
Chapter 936, "When Did the River Moon First Shine on People [Extra: River Moon Chapter]", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event.
Chapter 640, "Fanning the Flames Combo", is the clearest early answer because it turns Zhao Lang's situation into a concrete plot event. The chapter gives readers a real answer by opening on Jiang Li choked up even more.
Chapter 797, "Bu Fan and Bu Chen", is the clearest early answer because it turns Mom's situation into a concrete plot event. A useful checkpoint is the way the scene starts with The night grew deeper, and while waiting for news, Jiang Li dragged...
Chapter 813, "She Has a Child?!", is the clearest early answer because it turns Jiang Cheng's situation into a concrete plot event. A useful checkpoint is the way the scene starts with In the past, he might have helped Meng WanZhi speak.
Chapter 795, "Trouble Befalls the Third Lady!", is the clearest early answer because it turns Jiang Shixu's situation into a concrete plot event. Early on, The group photo was spreading like wildfire on Weibo.. By the end, Jiang Yan dumped all the bottles he'd taken out into the arms of the....
The best chapter pointer here is Chapter 11, "She Smiled, He Panicked". It opens with After a meeting, Shang Shaojing pinched the bridge of his nose, tired, and... and closes on Miss Qin, please accompany us to the police station to explain this....
Chapter 852, "Could That Be an Aphrodisiac Spell?", is the clearest early answer because it turns Red Chalcedony's situation into a concrete plot event. The chapter gives readers a real answer by opening on Rong Junsheng's words startled Shi Lei and Rong Kexi.