In the Naruto universe, the idea of Naruto killing Jiraiya is quite shocking. The normal Naruto we know would never do such a thing. However, in a fanfic, the writer might create an alternate reality where Naruto is somehow corrupted or deceived. Maybe an evil force takes over Naruto and makes him attack Jiraiya. But again, this is not in line with the core values of the Naruto series, and it's likely that such a fanfic would be controversial among fans.
There may be some very niche or dark 'naruto kills jiraiya fanfic' out there, but it's not a mainstream concept. Naruto and Jiraiya have a strong bond in the official story. Jiraiya is Naruto's mentor, and Naruto looks up to him. So for Naruto to kill Jiraiya would require a very extreme and uncharacteristic set of circumstances in a fan - created story, like some sort of mind - control or extreme misunderstanding that forces Naruto's hand, but this is all very far - fetched.
I'm not aware of a common 'naruto kills jiraiya fanfic'. In the original Naruto series, Naruto respects Jiraiya deeply. Such a plot would be a huge deviation from the canon and go against Naruto's character. It's hard to imagine a legitimate story where Naruto would kill Jiraiya.
One possibility could be that Jiraiya is under the influence of a powerful enemy's jutsu that makes him lose control of his actions and accidentally attacks Naruto. This could lead to a great deal of guilt and self - loathing for Jiraiya later.
There might not be a legitimate 'harry kills all purebloods fanfic' in the mainstream fanfic world. The Harry Potter universe is built on the values of equality and co - existence among different magical beings. A story where Harry kills all purebloods would not only be out of character for Harry but also create a very negative and untrue representation of the world J.K. Rowling created. It would be a very radical departure from the original series' message of hope and the power of love over hate.
One possible reason could be mind control. Some dark power might take over Naruto's mind and force him to turn on Jiraiya without his own will.
There could be a 'naruto kills jiraiya fanfiction'. It could be based on a time - travel scenario. For example, if Naruto from the future travels back in time and somehow his actions cause a chain of events that lead to Jiraiya's death. Or perhaps there's a dark, alternate universe where Naruto's values are twisted and he sees Jiraiya as an obstacle to his new, malevolent goals and thus kills him.
Perhaps in this fanfiction, Jiraiya discovers that Naruto is going to be the cause of a major catastrophe in the future. He might have seen a prophecy or some sort of sign that convinces him Naruto has to die to prevent this. It could also be that Jiraiya has been misled by false information about Naruto, which makes him think that Naruto has become an evil force that needs to be eliminated.
It can create a sense of growth for Naruto. Without Jiraiya by his side, he has to rely more on his own instincts and the skills he has already acquired. This can lead to new character development as he faces challenges alone.
It would be quite a shock to the Naruto fandom. Jiraiya is a beloved character and Naruto is the protagonist. For some fans, it would be a very dark and disturbing concept. It might make some fans angry as it goes against the typical relationship and character development in the original series.
One possible plot could be that Naruto goes on a special training journey with Jiraiya again, but this time they encounter a new and powerful enemy that has a connection to Jiraiya's past. Naruto has to learn a new jutsu from Jiraiya to defeat this foe.
One possible plot could be that Naruto has been misinformed about Jiraiya's actions. Maybe he heard false rumors that Jiraiya was involved in something bad. So, he decides to ignore Jiraiya out of disappointment. As a result, Jiraiya has to find ways to prove his innocence and regain Naruto's trust.
I'm not aware of any legitimate 'naruto kills sakura fanfic' in the mainstream Naruto fan community. This goes against the general nature of the Naruto series where the characters are friends and comrades. Most fanfics focus on positive relationships and adventures among the characters.