luffy yells

Mrs Black could be so offended that she starts to plot against Hermione. For example, she might try to get Hermione into trouble with the Hogwarts authorities by spreading false rumors about her.

Harry might become more determined to prove Snape wrong. He's a stubborn character, and Snape's yelling could fuel his desire to show that he's not the misbehaving student Snape seems to think he is.

Perhaps in the fanfic's storyline, Tony is facing a lot of pressure himself, like threats from powerful villains or issues within the Avengers. Peter's actions, whether they are mistakes or just inconvenient timing, could be the straw that breaks the camel's back for Tony, causing him to yell at Peter.

Bastian.

Perhaps Ruby made a decision that Weiss strongly disagreed with regarding a mission objective. Ruby thought it was a good idea to help a group of civilians first, but Weiss believed they should focus on the main target. Weiss would yell, 'Ruby, you're being naive! We can't deviate from our mission just for some strangers!' This would start a heated debate between them, with the other team members having to step in to calm them down.

I think it's 'Falcor' that Bastian yells. It's a key name in the story.

There could be many potential authors. It might be a fan who is really into the relationship dynamic between Bruce and Dick. They could be someone who has been following the comics or other media where these characters appear for a long time.

Maybe Bruce yells at Dick because Dick made a dangerous decision during a mission without consulting Bruce first. For example, Dick might have put himself in harm's way to save a civilian but in a way that violated the team's protocol.

One possible reason could be miscommunication. Maybe Ginny did something without fully explaining her intentions to Harry, and in the heat of the moment, he yells. For example, if she made a decision about their relationship without consulting him first.

Another possibility is a new character. This new character could be causing trouble between Sonic and Tails. For instance, the new character might be spreading false rumors about Tails, which makes Sonic angry at Tails.