Naruto could try to talk her out of it. He is a firm believer in the power of friendship and words. So, he would likely use his words to try and break whatever spell or wrong idea is in Sakura's head that made her want to kill him.
He may also try to defend himself without hurting Sakura too much. Given his kind - hearted nature, he would not want to seriously harm Sakura even if she is trying to kill him, so he would find ways to just hold her off until she comes to her senses in the fanfiction.
Some fans are horrified. They love the characters as they are in the original series and any deviation that involves such a violent act against a main character like Sakura is unacceptable to them.
It could be due to a dark influence. Suppose she was under the influence of some dark magic or an evil force that made her lose her true self and turned her against Naruto. This could lead to her almost killing him in the fanfiction.
Sasuke would likely be filled with rage. He and Naruto had a complex relationship, and Naruto's death at Sakura's hands would make Sasuke seek revenge or at least demand answers. Kakashi, on the other hand, would be deeply saddened. He was Naruto's teacher and would probably feel a sense of failure.
There could be. Fanfiction allows for a wide range of interpretations and alternate storylines. But it's a really extreme and disturbing concept considering the bonds that Naruto, Sakura, and Sasuke share in the official story. It would be a very different take on the characters, and most fans who love the original story would probably find it hard to accept.
Sakura might be in shock at first. Unable to believe that Naruto, who has always been so strong - willed, could have ended his own life. As she processes it, she could become angry, not at Naruto but at herself and the situation that led to this tragic outcome.
One possible reason could be a misunderstanding. Maybe Sakura is under the influence of some dark magic or mind - control in the fanfiction, which makes her lose her rational judgment and attack Naruto. Another reason might be a strong emotional outburst. For example, if she discovers something she believes Naruto has done wrong, but in fact it's a misinformation, and her anger gets the better of her, leading to her almost killing Naruto.
Another character could come to his rescue. For instance, Sasuke might show up at the crucial moment. Despite their complex relationship, Sasuke still values Naruto as a friend or rival. He intervenes and stops Sakura from killing Naruto. Or perhaps Kakashi, Naruto's teacher, arrives in time. He uses his Sharingan or some other jutsu to neutralize Sakura's attack and save Naruto.
Naruto could also feel a deep sense of hurt. After all, he has been through a lot with Sakura. In the face of her betrayal, he might start to question his own judgment of people. However, being Naruto, he would not give up easily. He might try to find a way to redeem Sakura or at least make her see the error of her ways. He would draw on his own experiences of being ostracized in the past and use that to try to understand her actions and find a solution.
Naruto might be very forgiving right away. He has always had a big heart and cared deeply for Sakura, so he could just accept the apology with a big grin and say it's all in the past.
One common theme is self - doubt. Naruto may doubt his worth as a ninja or a friend, feeling like he has let everyone down. Another theme is the burden of his past. All the hardships he has faced can pile up and seem overwhelming, pushing him towards self - destruction.