He might also get angry. Peter has a strong sense of justice. If he feels that the Avengers are being unfair, he could stand up to them. He'll use his quick wit and his powers to show that he's not going to be pushed around easily.
Well, it could be through his words. He might say sarcastic or cutting remarks to Percy. For example, he could make fun of Percy's abilities or how he does things in a really mean - spirited way.
The meanness of Rennee can also drive the plot forward in relation to Bella. It might force Bella to find new allies or develop new skills to deal with Rennee. For example, if Rennee spreads rumors about Bella, Bella might have to learn how to defend her reputation, which can be a major part of her character growth in the fanfiction.
She could stand up to him. Hermione is known for her intelligence and quick - wittedness. So she might use her sharp tongue and logical arguments to put Draco in his place. For example, she could expose his wrongdoings or the flaws in his pure - blood ideology.
One possible reason could be jealousy. Maybe Peter has some natural talent or ability that Tony wishes he had, and this makes him mean. For example, if Peter is really good at something like coming up with innovative ideas quickly, and Tony, who is used to being the smartest in the room, feels threatened.
One possible reason could be a misunderstanding. Maybe Peter accidentally gets involved in something that looks bad to the Avengers, like being in the wrong place at the wrong time during a security breach. So they misjudge him and are mean as a result.