Deku might be initially shocked. He's used to Bakugou's aggression, but an actual injury is different. He could be in pain and disbelief at first. Then, he might try to downplay it, especially if he doesn't want to cause trouble for Bakugou, because Deku is generally a very forgiving character.
The accident could also have an impact on the overall dynamic of their friend group. Their friends might take sides, some feeling more sympathetic towards Deku and being angry at Bakugou, while others might understand it was an accident and try to mediate. This could create tension and interesting plot developments in the fanfiction.
The theme of growth is also very common. Both characters experience growth in different ways. Bakugou grows in terms of his emotional intelligence and how he treats others, especially Deku. Deku grows in his ability to stand up for himself and not let Bakugou's words and actions break him. And there's often a theme of communication too. How their lack of proper communication has led to the situation and how better communication can solve their issues.
One popular 'bakugou hurts deku fanfiction' is 'The Pain Between Us'. It delves deep into the complex relationship between Bakugou and Deku, exploring how Bakugou's actions can sometimes cause emotional harm to Deku. Another is 'Scars of Words' which shows how words from Bakugou can cut deep into Deku's self - esteem.
One possible motive could be a long - held grudge that has festered over time. Maybe Bakugou's constant bullying in their past finally pushed Deku over the edge. Another could be some sort of mind - control or dark influence that made Deku act out of character.
Bakugou could use his words. He might tell Deku that he believes in him. For example, he could say 'Deku, you may be a nerd but you're a strong nerd.' It's a backhanded compliment but it shows he has faith in Deku.
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.
Bakugou may prove his love by being protective. He might put himself in danger to save Deku. In many stories, this kind of self - sacrifice is a strong indication of love. Also, he could start to understand Deku's dreams and support him in achieving them, which is a deeper form of love than just friendship.