Bakugou might react with his usual anger. He could lash out at the bullies verbally or even physically, which might make the situation worse. For example, if someone makes a snide comment, he could respond with a loud and aggressive retort.
Bakugou might be initially shocked. He's used to Izuku calling him 'kacchan' for so long that it's become a normal part of their relationship. So, when Izuku stops, it could throw him off balance.
Some characters might try to understand Deku's motives. Kirishima, who was close to Bakugou, would be angry at first but might also try to find out if there were any extenuating circumstances. However, many would be afraid of Deku, seeing him as a threat now that he has killed one of their own.
Deku might be completely shocked at first. Since Bakugou has always been so aggressive towards him, he would never expect such a confession. He might just stand there, mouth agape, not knowing what to say.
In this fanfiction, some Avengers might be in shock. For example, Captain America could be deeply saddened, his belief in justice and protecting the world shaken. He might feel a sense of failure for not being able to prevent the Snap.
It gives fans a chance to explore different 'what - if' scenarios. By seeing the Avengers' reactions, fans can get a deeper understanding of the characters.
Tony Stark might use his quick wit and technology. He could immediately scan Peter to make sure there's no physical danger causing the hyperventilation. Then he'd probably crack a joke to try and calm Peter down, like 'Kid, you breathe any faster and you'll fly away like a human jetpack.'
Some characters would likely be entertained. For instance, Loki might enjoy seeing the various ways fans write him as a more complex anti - hero. He'd probably find the creativity in the fanfiction quite appealing.
It can also be frustrating at times. Some fanfictions lack the proper understanding of the movie's lore. They might introduce concepts that don't fit well with the established Marvel Cinematic Universe. But on the positive side, many fanfictions are a labor of love. Authors pour their passion for the movie into their writing, and that can really shine through, especially when they capture the essence of the characters as we know them from the movie.