Perhaps there was a competition or a mission gone wrong. In a high - stakes mission, if Kiba made a mistake that Naruto thought would endanger the whole team, Naruto's sense of responsibility might lead him to take extreme measures. Or in a competition, if Naruto got overly competitive and lost control, it could result in him almost killing Kiba.
It could also be due to an outside influence like a genjutsu placed on Naruto. A powerful enemy could have made Naruto see Kiba as a much greater threat than he actually is. So, in the heat of the moment, Naruto uses excessive force. Another factor could be Naruto's own inner turmoil. If he was really stressed or dealing with some personal issues, his control over his power might slip, and Kiba could end up in the line of fire.
One possible reason could be a misunderstanding during a battle. Maybe there was some sort of jutsu misfire or misinterpretation of an attack. For example, if Kiba was using a new and powerful technique that Naruto didn't recognize, Naruto might instinctively go all - out in self - defense, nearly killing Kiba.
One possible reason could be a misunderstanding. Maybe Sasuke is framed for something really bad, and Naruto, in his anger and sense of justice, lashes out without knowing the truth. For example, if there's a false rumor that Sasuke has attacked the village again, Naruto might be quick to act.
Their relationship would likely become very strained. Kiba would probably be afraid of Naruto at first. He might avoid Naruto and have a hard time trusting him again. Naruto, on the other hand, would feel extremely guilty.
One possible reason could be that Root has some evil plans that directly threaten Naruto's friends or the village. Naruto, being the protector, has no choice but to take them down. For example, if Root was planning to assassinate the Hokage and Naruto found out, he would fight back and might end up killing some of their members.
One possible reason could be a simple rivalry that has boiled over. Maybe they were competing for the same mission, and Naruto's determination to prove himself got the better of him. He might have seen Kiba as a threat to his goal of becoming Hokage, thinking that if Kiba succeeds in a high - profile mission, it could overshadow his own achievements.
Perhaps Naruto has a newfound confidence or a change in his personality that makes Kiba and Issei twitchy. In the fanfic, if Naruto starts acting more recklessly or assertively than usual, it might make them nervous. It could also be that Naruto has some sort of connection to an enemy or a dark force that Kiba and Issei sense, and that's what is making them twitchy.
One possible plot could be that Naruto, in the heat of a battle, somehow acquires Kiba's blades. He then has to quickly learn how to use them effectively against an enemy. Maybe he combines his own chakra - based attacks with the physical power of the blades.
Well, it could be a dark AU (alternate universe) where Naruto is pushed to the brink. Maybe he discovers some great betrayal among his friends and village. So in his rage, he decides to take revenge and starts killing everyone. But this is a very extreme and uncharacteristic concept for the original Naruto character.
Well, one possible plot could be that Naruto is betrayed by Konoha in some extreme way. Maybe he discovers some dark secrets about the village leadership that involve using him as a tool all along. This betrayal could push him to the edge and make him turn against Konoha, leading to a situation where he kills those who he feels have wronged him.
A misunderstanding is also likely. Maybe Kiba overhears a conversation that he misinterprets. For instance, he might think Hinata is talking badly about him when in fact she is just discussing a general ninja problem. This could make him angry enough to hurt her, either with words or actions.
One possible plot could be that Naruto is forced into a situation where he has no choice but to kill Haku in self - defense. Maybe Haku is under some kind of mind control and attacks Naruto relentlessly.