His anger often manifests physically. His muscles might bulge more than usual, and his hair could stand on end even more in his Super Saiyan forms. His ki, or energy, also becomes more visible and intense. It's like a red - hot aura surrounding him.
In some 'Goku Gets Angry' fanfiction, a common scenario is when his friends are in danger. For example, if Vegeta is seriously injured by a powerful new enemy, Goku's anger flares up. He then enters a new and more powerful form to fight the foe. Another scenario could be when the Earth is threatened. Maybe a villain plans to destroy the planet, and Goku gets angry at the thought of his home and family being in jeopardy. This anger gives him the motivation to train harder and find a way to defeat the villain.
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.
Natsu was looking forward to a delicious meal at the guild. But when he found out that someone had eaten all of his favorite food, his anger flared up. 'Who did it?' he growled, his eyes darting around the guild hall. No one answered, which only made him angrier. His nostrils flared as he stomped around, demanding answers. Erza tried to calm him down, but Natsu was beyond reason at this point. 'I'll find out who it was and they'll pay!' he shouted, his voice echoing through the hall. His hair seemed to stand on end as his anger reached new heights.
It could be Vegeta. Maybe Vegeta does something really underhanded like stealing Goku's senzu beans or trying to take all the credit for a victory that Goku also contributed to. Goku, being a fair - minded person, would get angry at such behavior.
One reason could be ChiChi's overbearing nature. She is often very strict about Goku's training and how he spends his time. In fanfiction, this could be exaggerated to the point where Goku finally gets fed up. For example, if she constantly nags him about not doing enough chores around the house instead of training, it might push Goku to his limit.
One possible reason could be a misunderstanding. Maybe Deeks misinterprets something Kensi says or does, leading to his anger. For example, if Kensi takes on a dangerous mission without consulting him, he might get angry out of concern for her safety and this could escalate into a fight.
Well, perhaps in the fanfiction the Hogwarts staff might have been unfair in grading his exams. Like giving him lower marks than he deserved just because they had some sort of prejudice against him. It could also be that they wrongly accused him of something he didn't do, like misbehaving or cheating. Another reason could be that they failed to protect him or his friends from some sort of danger at Hogwarts.
Well, sometimes in these fanfictions, Kuroko might get angry when his plans on the court are constantly disrupted. He's a strategic player, so if his teammates don't follow his lead or if the opponents manage to anticipate and counter his every move, it could push him over the edge. Also, if there's a situation where the team is about to lose because of someone's negligence, Kuroko's anger might flare up as he has a strong desire to win and see his team succeed.