This aggressiveness actually comes out now in UA as opposed to back in middle school and before that. Before, everyone praised him and no one was on his level so he really wasn't made fun of and his ego was being boosted to no end. Deku also annoyed him but for the most part Deku also wasn't standing out as much. Besides the time when they were kids, they probably weren't constantly interacting unless Deku said something outrageous like aimimg for UA or the like. He wasn't actively bullying Deku all the time as Deku is also seen going around fine without getting picked on. Now, he's constantly being made fun of and is being shown how he's not as special as he thought he was. You then get the inferiority complex that follows that along with a temperament prone to snapping quickly always being there and now you've ended up with the unpleasant guy that is Bakugou. That along with Horikoshi liking characters like Bakugou because of how easily he can write them. I'd say he has more fun writing Bakugou than he does Deku, though he puts more of himself into Deku.
The characters in Golem Hearts are currently very thin. This will definitely be expanded on in future chapters but the guy whose daughter was kidnapped made a heel turn too quickly. One second he's out to get Noah, the next, "Please save my Daughter!". Even in pinch situations like that, someone that just lost their cargo because of the individual in person and is out to get them for that, they will not suddenly turn around that quickly. It usually takes more prodding and a begrudging plea for help, even if your daughter is on the line. You wouldn't trust the first individual that quickly and would rather do something about it by yourself. Having Noah come in and then convince him to leave it to him while struggling would have made for better characterization. It would have shown how he really wants to help others.
