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.
The relationship could start with hatred. Bakugou may initially be enraged that Deku has become a villain. But as time passes, he starts to see the reasons behind Deku's transformation, which could lead to a more complex relationship.
Growth is also a prevalent theme. Both characters are on a journey of self - discovery and improvement, and fanfics usually show how they grow both as individuals and in relation to each other. For example, Bakugou learning to control his temper and Deku becoming more confident.
One common theme is rivalry. Their intense competition to be the best hero is often explored, like in many fanfics where they constantly try to outdo each other in training or in real battles. It shows their determination and drive.
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.
One positive aspect is their mutual growth. Their rivalry pushes them both to be better. Bakugou's aggression makes Deku strive harder to prove himself, and Deku's constant progress forces Bakugou to not fall behind.
One possible plot is that Bakugou has been secretly in love with Deku for a long time. He observes Deku's kindness and growth, and it makes his heart flutter. He decides to propose when they are alone one day. He might start by reminiscing about their journey together, from being rivals to becoming something more, and then pop the question.
The main characters are Bakugou and Deku. Bakugou is often portrayed as a brash and confident character, while Deku is kind - hearted and determined. In this fanfic, their relationship takes a romantic turn with Bakugou being the one to propose.
I really like 'Deku and Bakugou: A New Chapter'. It takes place after the main events in the series and explores how they face new challenges together. It's a bit of a slow - burn in terms of their relationship development, but that makes it all the more satisfying when they finally start to understand each other on a deeper level.