Often, in fanfictions, power struggles can lead to Boruto hurting Naruto. If Boruto becomes too power - hungry and Naruto tries to stop him from going down a wrong path, Boruto might see it as Naruto trying to keep him weak. This can lead to conflict between them. Also, there are times when Boruto blames Naruto for the death of someone close to him (even if it's not Naruto's fault), and in his anger, he hurts Naruto.
In the story, if Sarada hurts Boruto, it could shatter the fragile peace that the Naruto universe has achieved. Their generation was supposed to carry on the legacy of peace established by Naruto and the others. If this bond is broken, it could open the door for old enemies or new threats to emerge. The other young ninjas might also lose faith in their comrades, leading to a breakdown in teamwork. This could ultimately put the entire Naruto universe at risk as they are no longer united against potential threats.
In certain fanfictions, a possible plot twist is that Sarada is forced to choose between her loyalty to the village and her friendship with Boruto. If she believes that Boruto's actions are endangering the village, she might end up hurting him. For example, if Boruto is involved in some sort of forbidden jutsu research that the village sees as a threat, and Sarada is put in a position to stop him by any means necessary, including using force.
Physically, Naruto can use his Rasengan or other powerful jutsus to fend off enemies attacking Boruto. His combat skills are top - notch, and he won't hesitate to engage in battle to keep Boruto safe.
In the 'boruto kills naruto fanfiction', a motive could be a power struggle. Boruto might believe that Naruto's power is holding back the village's growth or his own potential. He could think that by eliminating Naruto, he can bring about a new era of power in the Hidden Leaf. Also, it could be out of desperation. If Boruto is in a situation where he believes that killing Naruto is the only way to save someone he loves, like his mother or a friend, he might take such a drastic step.
Maybe it's the high expectations that Naruto has for Boruto. Naruto is a hero, and he might unknowingly put a lot of pressure on Boruto to follow in his footsteps. Boruto could be scared of not being able to meet those expectations.
They could start by having an honest conversation. Naruto could sit down with Boruto and just listen to his fears without judgment. This would be a first step in building a better relationship.
Boruto's reaction would be complex. He'd be heartbroken, for sure. He might start to question his own worth and purpose. But over time, he'd realize that he has to carry on Naruto's legacy. He'd become more serious and focused. He'd also become more empathetic towards others, understanding the weight of sacrifice. He might even start to study Naruto's techniques and leadership style more closely, trying to emulate the things that made Naruto such a great Hokage and hero.