A great antagonist could be a corrupted teacher. For instance, a teacher who is secretly working for Voldemort but has been hiding in plain sight at Hogwarts for years. They could manipulate the Triwizard Tournament to their own ends, causing all sorts of trouble for Harry and his friends.
Another option is an evil version of one of Harry's friends from an alternate dimension. Imagine if Ron was turned to the dark side in this AU. He would know all of Harry's secrets and weaknesses, making him a formidable and unexpected enemy in the fourth - year events.
It could also be a powerful dark wizard from a foreign school that was not supposed to be part of the Triwizard Tournament. This wizard has his own agenda, which involves stealing powerful magical artifacts from Hogwarts during the chaos of the tournament and will stop at nothing to achieve his goals, even if it means going against Harry Potter.
Chapter 441, "The Taoist also Chases Stars?", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. The chapter turns that into something concrete by moving from She had also only learned a little trick after reading many books.
Chapter 185, "We Are the Real Team", is the clearest early answer because it turns Su Yinwan's situation into a concrete plot event. Early on, He was so anxious that he immediately picked up the megaphone.. By the end, The next, she'd complain that the ground was too slippery to walk on..
Chapter 187, "I Really Need an Apology", is the clearest early answer because it turns Su Yinwan's situation into a concrete plot event. Early on, During the competition, she passed by him numerous times, unfazed by.... By the end, Perhaps it was a pig that tripped you;
Chapter 356, "I announce, Lili is the best of the night!", is the clearest early answer because it turns Lili's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Seeing such a bustling scene, Su Yinwan who had just alighted from...
Chapter 254, "Madwoman! She is definitely a madwoman!", is the clearest early answer because it turns Jiang Yan's situation into a concrete plot event. Early on, Just when everyone thought that Jiang Yan wouldn't last long and....
Chapter 304, "Shh, Let's Not Disturb Big Sister", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. It opens with But his cries and screams didn't elicit the slightest sympathy from...
Chapter 347, ""I Want to be the Eagle in the Wilderness", is the clearest early answer because it turns Zhang Cheng's situation into a concrete plot event. A useful checkpoint is the way the scene starts with On the way there, Jiang Li had already learned quite a bit about the...
Chapter 438, "The Upper Stream is Mine, The Lower Stream is Yours", is the clearest early answer because it turns Sister Li's situation into a concrete plot event. Early on, I'm sorry," Shang Shuyue squeezed out three words through clenched....
Chapter 85, "They must have been bought off by Jiang Li!", is the clearest early answer because it turns Chixia Village's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Facing everyone's skepticism and curiosity, Jiang Li explained...
Chapter 369, "Who Makes Him the Omnipotent Male Lead?", is the clearest early answer because it turns Lin Manru's situation into a concrete plot event. Early on, But..." Lin Manru's tone shifted again, "Our studio has become....