Well, perhaps in the fanfic, Orochimaru tortures Naruto as a form of revenge against the Leaf Village. He might use his various snake - related jutsu to cause pain and harm to Naruto. For example, he could make snakes constrict Naruto, slowly squeezing the life out of him while also injecting him with some sort of venom that causes excruciating pain. And all this while, Naruto is trying to find a way to break free and defeat Orochimaru, relying on his inner strength and the memories of his friends and his training.
In this type of fanfic, it could be that Orochimaru is trying to break Naruto to make him his new apprentice. He tortures Naruto not just physically but also emotionally. He might show Naruto false images of his friends being killed by the Akatsuki, which would be a huge mental torture for Naruto. Orochimaru could also use his knowledge of forbidden jutsu to manipulate Naruto's chakra in a painful way. Naruto, on the other hand, would be constantly fighting back, using his willpower and the unique abilities he has, like the shadow clones, to try and outwit Orochimaru.
One possible plotline could be Naruto being captured by Orochimaru and forced to endure various genetic experiments. Maybe Orochimaru is trying to extract the power of the Nine - Tails from Naruto in a more invasive way. Another could be that Naruto's friends, like Sasuke and Sakura, attempt a daring rescue mission while Naruto is in Orochimaru's clutches and they face off against Orochimaru's minions.
Well, in such a fanfic, a plotline might involve Naruto's friends trying to rescue him. They could discover Orochimaru's lair where Naruto is being experimented on. Meanwhile, Naruto himself could be developing new and unexpected powers as a result of the experiments, which he then has to learn to control. And there could be a race against time for Naruto's friends to reach him before Orochimaru's experiments cause irreversible damage.
A possible plotline could be Orochimaru's redemption. He realizes the error of his ways and joins Naruto in protecting the ninja world. He could use his vast knowledge of jutsu and forbidden arts to help Naruto against new threats.
He could develop post - traumatic stress disorder (PTSD). Flashbacks of the torture might haunt him during battles or normal daily activities. This would not only affect his performance as a ninja but also his personal relationships. Naruto might become withdrawn as a result of the torture. He might isolate himself from his friends and the village in an attempt to protect them from any potential harm that could come his way because of his association with Orochimaru through the torture. This isolation would further damage his mental state as he thrives on the support and friendship of those around him.
Perhaps Naruto starts to have a connection to Orochimaru's other experiments or creations. He might find himself in a situation where he has to either help or fight these other 'products' of Orochimaru's mad science. Also, the fanfiction could explore how Naruto's friends react to what has happened to him. Do they trust him still? Or are they afraid of what Orochimaru might have turned him into?
One possible plotline could be Harry being held captive in one of Voldemort's dark lairs. Voldemort might use the Cruciatus Curse on him repeatedly to try and break his spirit or get information about the Order of the Phoenix. Harry could be isolated and tortured while his friends desperately search for him.
Naruto might resist through his strong willpower. He has always been determined, and this would not change even under torture. He could keep thinking about his friends in the Leaf Village and his goal of becoming Hokage, which gives him the strength to endure.
Another plotline could be a more psychological exploration. Orochimaru has always been a bit of an enigma, and his love for Naruto could be a way to explore his own humanity. Maybe he has a change of heart because of Naruto and starts to question his past actions. This could lead to a journey of self - discovery for Orochimaru, while Naruto is left to figure out how to deal with this new side of his old enemy.
A plotline could be Percy having to face his own fears and insecurities while being tortured. Maybe he starts to doubt his abilities and heroism. But as the story progresses, he overcomes these doubts through his willpower. Also, the fanfic could explore how the torture affects his relationship with the gods. He might feel betrayed by them for allowing him to end up in Tartarus and this could lead to a change in his loyalty or attitude towards them.
In this fanfic, it might be that Fleur has been wrongly accused of a crime by a powerful magical authority. Harry tries to defend her but is captured instead. The authority tortures Harry to force him to give up on Fleur. However, Harry refuses. He endures the physical and mental pain of the torture. His perseverance might inspire some of the other characters to see the truth. Eventually, they join forces with Harry and they manage to expose the real culprit and save Fleur.