Perhaps Hades could be an antagonist in this fanfiction. He is often at odds with Percy in the original Percy Jackson stories. Now with Percy having Superman - like powers, Hades might feel that Percy is getting too powerful and could potentially disrupt the balance in the underworld. Also, the villains from Superman's world like Metallo could be brought into this story. Metallo, with his kryptonite - based powers, could pose a serious threat to Percy if he manages to find a way to counter Percy's demigod and Superman - like abilities.
The main antagonists could be the Titans. They are powerful enemies in the Percy Jackson universe already. Now that Percy has Superman - like powers, they might see him as an even greater threat to their plans of overthrowing the gods. So, they would do everything in their power to stop him.
In this type of fanfiction, Darkseid could be a major antagonist. He is one of Superman's greatest foes. If he discovers that there is a 'son of Superman' in the world of Percy Jackson, he might try to invade that world to either capture Percy or use the power of the demigods for his own evil purposes. Also, some of the traditional demigod villains like Ares might also oppose Percy more strongly now. They might be jealous of his new powers and see him as a threat to their status among the demigods.
The best chapter pointer here is Chapter 266, "He Really Deserves to Die!". It opens with Upon hearing this, the deputy director's expression also turned serious. and closes on Now I see why Jiang Li despises her brother so much, utterly unreliable!"....
A practical answer is Chapter 248, because it turns the idea into a concrete scene. The chapter opens with Chixia Mountain in the early morning was still shrouded in a pale green..., adds pressure through In the next second, his smile froze on his face., and ends on Since we can't take the.
The best chapter pointer here is Chapter 261, "They've Ruined the Entertainment Industry!". It opens with The village chief's eyes nearly popped out after he heard the whole story. and closes on Is it necessary to be so guarded against me?.
Chapter 255 is the strongest chapter-level answer because it starts from Sounds pretty interesting." "I know this one! and follows through on He was wearing a dark red traditional jacket with exquisitely carved....
A practical answer is Chapter 259, because it turns the idea into a concrete scene. The chapter opens with While the villagers of Chixia Village were all immersed in the revelry of..., adds pressure through Wasn't she the same girl who had come to them with a group of villagers..., and ends on It.
The best chapter pointer here is Chapter 236, "The Murderer Returns to the Scene of the Crime Theory". It opens with The short-haired youth beside them chimed in, "That's right, senior, we... and closes on Everyone, try not to get too anxious." The crowd nodded, seemingly....
Chapter 218 is the strongest chapter-level answer because it starts from However, what surprised the guests even more was that the harvest Director... and follows through on Thinking about this, Jiang Yan started to feel his buttocks ache again; he....
The best chapter pointer here is Chapter 241, "Thieves Will Shed Two Tears When They Break In". It opens with It wasn't the director," Jiang Yan said with a blank expression, "Did you... and closes on However, as he turned around, before he could see the person properly, a....
A practical answer is Chapter 223, because it turns the idea into a concrete scene. The chapter opens with So, for the first time, Jiang Yan, who had always styled himself as the..., adds pressure through He could simply have someone send a flurry of gifts and make some..., and ends on The damned.
The best chapter pointer here is Chapter 231, "vLet Me Check Out the Strength of 5000". It opens with Huo Xuan felt a burst of secret delight in her heart. and closes on A cool sports car was one hundred thousand bucks..