Describing his body language is crucial. When Tony is angry, his shoulders might tense up, his fists clench, and his eyes narrow. He could be pacing back and forth rapidly, or standing still but with a menacing look on his face. The author can also mention how his voice changes, perhaps getting deeper or more gravelly when he's angry.
The author can use strong dialogue. For instance, having Tony shout out angry words with a lot of force and passion. Words like 'I've had enough!' or 'You'll pay for this!' can quickly convey his anger. Also, the use of expletives (if appropriate for the rating of the fanfiction) can enhance the sense of his fury.
Showing the consequences of his anger is an effective way. If Tony is angry at a fellow Avenger, he might start a fight or use his technology in a more aggressive way. This not only shows his anger but also how it affects the relationships around him. For example, if he lashes out at Rhodey in anger, it could damage their friendship and create a rift that other characters have to try to mend.
Show his internal thoughts. Let the readers see what he's really thinking and how it differs from what others think of him. For example, when he's creating a new piece of tech, have him worry about how it will be misused even though others might assume he's just doing it for fun.
They can describe his physical symptoms clearly, like his hands shaking, sweating profusely, and his breath coming in short gasps. This gives a vivid picture of the panic attack.
Writers can show his recovery through his interactions. For example, if he's more irritable with his friends at first due to the pain and confusion from the concussion, and then gradually becomes more like his old self. That would be a good way to portray the recovery process.
The author can use physical cues. For example, Kuroko might clench his fists tightly, a rare display of emotion from him. His normally calm blue eyes could narrow and become more intense. Another way is through his dialogue. He could speak in a sharper tone than usual, with shorter, more forceful sentences.
Well, obviously Tony Stark himself is the central character. Pepper Potts often shows up as she is close to Tony and can either calm him down or be on the receiving end of his anger in some cases. Rhodey is also common as his friend and military contact. He might try to reason with Tony when he's angry.
In some fanfiction, Tony Stark might be angry at the Avengers because of a perceived betrayal. For example, if they made a decision without consulting him that put him or the world in danger. He's a control freak in a way, so when things go awry without his input, he could get mad.
Writers can show Po's anger through his physical actions. For example, his fists clenching tightly, his face turning red, and his body tensing up. Just like how he might look when facing a really tough opponent in the movies. They can also use his dialogue. Po might start stuttering a bit more when angry as he tries to get his words out while being overcome with emotion. For instance, he could say something like 'You... you can't just do that!'
It might show a distant relationship. Tony could be physically present but mentally absent, not really engaging with his children on a deep emotional level. For instance, when they try to talk to him about their day, he might be half - listening while still thinking about his latest Iron Man upgrade.
There might be a fanfiction where Tony is angry with his fellow Avengers for some misunderstanding. He decides to go on a solo mission to prove his point, which leads to all kinds of adventures and self - discovery. In the process, we see his anger fuel his actions but also how he overcomes it in the end.
He might become more power - hungry. Usually, he is a hero, but with the goal of taking over the world, he could lose some of his moral compass.