Danzo could also be a main antagonist. He was always power - hungry and paranoid. Naruto having the Sharingan might make him feel that Naruto is becoming too powerful and unpredictable. So, he could try to eliminate Naruto or control him. Plus, Danzo has a history of using underhanded means to achieve his goals, and Naruto's new power would be a great target for his schemes.
It could be Orochimaru. Since he has always been interested in obtaining powerful abilities, he might see Naruto with the Sharingan as a threat and try to take it for himself.
Another possible antagonist could be a rogue Uchiha who is jealous that Naruto, an outsider, has gained the Sharingan. This Uchiha might feel that the Sharingan is a sacred power of their clan and should not be in the hands of someone who is not an Uchiha. So, they would try to take it back by any means necessary, even if it means fighting Naruto and his friends.
Chapter 331, "The Casual Video Went Viral?!", is the clearest early answer because it turns Went Viral's situation into a concrete plot event. The chapter gives readers a real answer by opening on At that moment in the He family.
Chapter 614, "Storm Crisis", is the clearest early answer because it turns Ji Yanbai's situation into a concrete plot event. It opens with Today, the wind on the island was stronger, and for safety reasons,... and closes on He slightly raised his head and met Pei Ye's dead eyes, his scalp....
Chapter 803, "Younger Brother Misses Mom", 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 Brother, do you think hiding here is a bad idea?" "Don't worry,...
Chapter 483, "Why Does a Pig Eat M9?!", is the clearest early answer because it turns Jiang Yan's situation into a concrete plot event.
Chapter 645, "Without Luck, You Are Nothing!", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Shang Shaojing furrowed his brow and fished out two banknotes from...
Chapter 627, "Definitely Not an Accident", is the clearest early answer because it turns Nina's situation into a concrete plot event. A useful checkpoint is the way the scene starts with He looked at the sinister smile lingering in Jiang Li's eyes, then at...
Chapter 809, "Specially Made for You", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. Early on, Listening to the cries from inside the house that sounded like a pig....
Chapter 449, "Do You Two Have to Be So Abnormal?!", is the clearest early answer because it turns Jiang Yan's situation into a concrete plot event. The chapter turns that into something concrete by moving from Ahhh, the young master's good looks have finally returned!" "Wuwuwu,...
Chapter 238, "The Guests Were Dumbfounded, The Audience Was Excited", is the clearest early answer because it turns Jiang Yan's situation into a concrete plot event.
Chapter 251, "It seems that going on a transformation show is really useful!", is the clearest early answer because it turns Sister Chen's situation into a concrete plot event. The chapter gives readers a real answer by opening on If Du Qinglian was somewhat angry just a moment ago, now she was...