One possible plot could be related to environmental issues. Italy is known for its beautiful landscapes. If other countries are not taking proper actions to combat climate change which is also affecting Italy's natural beauty, Italy could get angry. It might start its own initiatives and try to persuade other countries to follow suit, leading to a story full of challenges and cooperation.
Obviously, Italy itself would be the main character. There could also be other European countries like France and Germany. They might be the ones causing Italy's anger, or they could be Italy's allies trying to calm it down.
In this fanfiction, the caboose could get angry if it has a goal or a dream that is constantly being thwarted by the red vs blue conflict. Let's say the caboose wants to bring peace between the two sides but they keep ignoring its efforts. It tries to communicate but they just laugh at it or don't take it seriously. So all these rejections and lack of respect make it angry.
Well, perhaps in this fanfiction, Hermione moves to Italy to escape the chaos in the wizarding world she left behind. There, she starts a new life in a small Italian village. She could open a little magic shop where she sells potions and magical artifacts she's brought from England, while also learning Italian spells and incantations.
Danzo could also be the one to make Naruto angry. Danzo's underhanded tactics and secrets might be exposed in the fanfiction, and if they were to directly harm Naruto's friends or the village, Naruto would be furious at his actions.
After Natsu gets angry, the plot might develop with other guild members trying to mediate. Happy might try to calm Natsu down while Gray could be in the middle trying to make both sides see reason. This could create a lot of comical and tense moments in the fanfiction.
Well, one possible plot could be that the other nations have to take care of baby Italy. They might struggle with things like feeding him, changing diapers, and getting him to sleep. Maybe they also discover new aspects of Italy's personality that were hidden before.
Well, one possible plot could be that Italy's transformation into a girl causes chaos among the other nations at first. They are all used to his male self. But as time goes by, they start to see the new 'her' in a different light. Maybe 'she' brings a new perspective to diplomatic meetings or cultural exchanges. For example, the way 'she' approaches cooking and art might change a bit, adding a feminine touch to things that were previously more masculine in the eyes of the other nations.
It could be due to unfair treatment from teachers. For example, if he's blamed for something he didn't do just because he's a Saiyan or has special powers. Teachers might be prejudiced against him, which would lead to his anger. He's a good - hearted person but constantly being misjudged would surely get on his nerves.
Well, maybe Gohan gets angry because Hercule takes all the credit for saving the world when in fact Gohan did a lot of the real work. In fanfiction, the writer might play up this injustice, making Gohan seethe with anger at Hercule's false bravado.
One possibility could be that Serena gets angry when she is constantly overshadowed by other trainers in a big tournament. She might feel that all her hard work is being ignored, so she gets angry and decides to train even harder in isolation to prove herself.