If society is the reason for the personality of Bakugo, why aren't there more Bakugos in society?
If "strong" quirks turn people into violent a**holes, why aren't Nejire, Tokoyami, Kaminari, and that loud wind quirk guy relatively well-adjusted to social interaction.
The answer is simple: because it isn't society's fault.
Like, don't get me wrong, it didn't help, that's for sure, but Bakugou's problem isn't society, it's that he's a jerk. Bakugou is unironically high on his own brand.
Part of that is how other people treated him, true (though it was happening even before he had a Quirk, so it's not society in the way it's usually used for Bakugou, where it's about his Quirk), because he was cool and competent as a kid, which made the kids praise him, which fed his ego, which made him want to do it more, in a vicious cycle... but even with that, there's still something unique to him that is at fault here: he's told, as a kid, that he has a good Quirk, and he can be a hero with it. This is basic, bog standard encouragement; it's a good Quirk, but he's, what, ten? That woman is probably telling every single kid that their Quirk is great. But Bakugou, though, he hears this, and his mind instantly snaps to a conclusion: he realizes that he's The Best, TM. That he's special, that he's better than everyone else. And that? That's not 'society', that's not the fault of people around him, that's Bakugou's fault, Bakugou's problem.
I'll be honest here, kids are stupid; Bakugou isn't the first kid to have a delusion of grandeur and he's not going to be the last. What makes it different with him, though, is that it's more than just a passing phase. That philosophy, his fundamental superiority, is a train of thought that remains with him for the rest of his life, and not only that, it is a cancerous logic that festers in his mind like a disease.
You know how Bakugou calls everyone else 'Extras'? That's the logical conclusion of his superiority complex, of the idea of that he alone is special, superior, the honored one: because if he's special, what is everyone else? Less then him. An extra in his story. Or, as Shigaraki would put it?
That's concerning. More than that, that is deeply alarming. Unironically, I think that counts as a mental disorder of some form (probably narcissism?), and it also inherently dehumanizes other people... which explains why he's so casual about hurting everyone around them.
And to be blunt? That's a very, very bad thing. Dehumanizing other people is how people are taught that it's OK to hurt others, or even kill them; fundamentally, Bakugou is radicalizing himself against everyone who isn't Bakugou.
If they are less than him, if they are not 'real people', if they are just extras... then it doesn't matter if he hurts them, insults them, because... why would it? It's not like they're actually people, it's not like they're important. They're just extras in The Great Story Of Bakugou. They're just NPCs in the Hero Game he's playing, and nothing else.
People do horrible, horrible things to NPCs in video games that they would never in a million years do to people in real life. They do it because NPCs don't matter, not like real human beings do. Think, for a minute, how you treat the random characters in Fallout or whatever, the nameless mooks you that will always more of, because they will always respawn after whatever you do to them. Think about what would happen if you did that to a real person.
You can even see it in how he acts in the various flashbacks back when he was a child: when he was young, Bakugou was brash, a bit aggressive, but largely an OK kid. But as time passed, his aggression grew, and his respect for others shrunk. He went from insulting people (at times probably accidentally), to actively bullying them. He became more and more comfortable not just verbally abusing others, but then physically hurting them. By the time canon starts, Bakugou seemed to treat, and consider, other human beings as barely more than trash, and Izuku's existence in particular as something like a cosmic mistake he was 'graciously' tolerating.
And then we find out that he was willing, in fact, to kill people. It's very likely that, if driven to a corner, that people may be willing to kill to survive, but that isn't what happened to Bakugou: he was in school. He was unironically playing cops and robbers.
And yet, Izuku's basic unwillingness to just... give up, to just sit back and let someone maim him as much as he wanted is what 'cornered' Bakugou to the point he resorted to overwhelmingly lethal force. He doesn't feel an ounce of guilt about it afterwords, either, and he only stops because he's threatened... with being kicked out of the exercise. He's not even serious about, he's willing to kill someone but he values winning more than his murder attempt, winning at something that's essentially worthless, even. It's an impulse, one that he doesn't ever question or think about again after the fact.
To be fair, his... radicalization, or just plain assholishness, got noticeably cut back after that point (to the point where it seems more like retcon than character development), but if it wasn't for that? Clearly, no one was willing to call him on things before, so if he didn't get serious consequences, and he had killed Izuku? He probably would have grown more and more comfortable with killing, the same way he did with everything else he's done.
But it's more than just that. His parents are... well, they're good people, but... they don't seem to be the best at making their son not be an asshat; both of them were pretty OK with their son calling his mother a 'hag', and not even in a sarcastic, well meaning way, but as an actual insult.
His mom is cut from the same cloth as her son (normally, it'd be the other way around, but Bakugou's character probably came first), if more restrained. Unfortunately, that means she's probably a source of a lot of his more aggressive behaviors in the first place, and not just in a genetic way: he watched what she did, and then learned to do it from her. She tries to get him to stop the worst of it but she doesn't seem to making a serious effort? It's not a serious punishment, or a heart to heart talk about his behavior, it's... basiclly the fan gag, which doesn't really teach anyone anything?
His dad, meanwhile is more passive, grounded, but at the same time: he married Bakugou's mother. He's clearly OK with behavior in that vein. It's good he's not contributing to the problem, but he's not solving it, either.
At the end of the day, while there are contributing factors, not of them are enough to explain, much less justify, Bakugou's actions or personality. Society didn't make him like this. No one taught him that it was OK.
The only one with responsibility was Bakugou himself.
