Okay, so 'KamiDeku' tends to get all the intricate rival-to-lover analysis, but people sleep on how emotionally messy Bakugou and Denki can be. A lot of writers just throw them together for crack, but the good fics dig deeper.
A huge one is the friction between Bakugou's drive for absolute victory and Denki's more relaxed, social nature. Denki isn't a slacker, but he's not obsessed with being the best like Bakugou is. You'll see fics where Bakugou reads Denki's easygoing attitude as a lack of seriousness, and it makes him furious—partly because he can't stand 'wasted potential,' and maybe partly because Denki's happiness seems effortless. Meanwhile, Denki might feel like he can never measure up, that his intelligence or power will always be 'not enough' in Bakugou's eyes. That's fertile ground for both angst and growth.
Another layer is the whole 'circuit overload' metaphor for Denki's quirk and emotions. Fics love exploring Denki's fear of hurting Bakugou accidentally, of his power being something volatile and dangerous he can't perfectly control. Bakugou, whose own power is incredibly controlled violence, would have a complex reaction to that—disdain for the lack of control, but maybe a grudging understanding of the destructive force within. The conflict isn't just 'will they/won't they,' it's 'can they trust each other not to break under the strain?' I've seen some where Denki pulls back emotionally because he's scared, and Bakugou has to confront something that isn't a problem he can just explode his way through.