Sasuke could make Naruto pissed off if he goes back to his old ways of seeking power and revenge. Naruto has worked hard to bring Sasuke back to the right path, and if Sasuke strays again, it would surely anger Naruto.
A new, powerful and arrogant villain introduced in the fanfic could be the cause. This villain could constantly mock Naruto and his ideals, and try to undermine his efforts to protect the village. Such blatant disrespect would make Naruto really pissed off as he is very protective of his home and the values he stands for.
Sasuke could be the cause. If Sasuke were to betray Naruto again in the fanfiction, it would surely make Naruto pissed off. Their relationship is complex and Sasuke's actions have a big impact on Naruto.
First, the author should stay true to Naruto's character. By studying his traits like his determination, his loyalty to his friends, and his never - give - up attitude in the original anime. For example, don't make him a coward when he's known for being brave. Second, improve the plot. Make it more logical and in line with the Naruto world. No sudden, out - of - the - blue events that don't fit. Third, work on the writing quality. Use proper grammar and spelling so that readers can easily follow Naruto's journey in the fanfic.
One common theme is revenge. When Naruto is pissed off, often he's seeking revenge against someone who has wronged him or his friends. For example, if Orochimaru did something to harm Sakura, Naruto would be pissed off and his revenge - driven actions would be the focus. Another theme could be self - discovery. His anger might lead him to discover new powers or a new side of himself. Like his anger might unlock a hidden bloodline limit that he didn't know about before.
Maybe Naruto gets pissed off because his friends don't believe in him. For example, if they suspect him of being involved in something bad without evidence.
It could also be due to the fanfic's poor writing quality. If the grammar and spelling are atrocious and it's hard to follow the story. When it comes to Naruto, fans have high expectations. So, if they can't even understand what's going on with Naruto in the fanfic because of bad writing, it can lead to a 'pissed off' reaction.
A sense of powerlessness can also be a theme. When he's faced with situations where he can't immediately solve a problem or protect those he cares about, Harry might get pissed off. This often leads to him finding new ways to gain power or take control in the fanfiction.
Another reason might be related to his family. In some fanfictions, his parents' story or his relationship with his family members could be distorted. Harry has a strong connection to his family, especially his parents, and any wrong portrayal of that could make him pissed off.