My Hero Academia has featured some pretty incredible character development stories, and one of its best is Bakugo Katsuki's. From his introduction as an aggressive middle school bully to a Pro-Hero powerhouse worthy of facing the world's greatest villain, Bakugo has had a lot of growth in terms of physical strength, mental fortitude and moral development. Here's how his fight against Shigaraki Tomura ties up his character arc nicely.
There's no two ways about it; early MHA Bakugo was not a nice person. He routinely bullied Midoriya Izuku and his attitude only worsened when they both made it into the prestigious UA. Bakugo placed so much importance on his Quirk, believing its power made him invincible and that he had no need for others. Having the highest admittance score among all the first years did little to temper his superiority complex. He started referring to his classmates and colleagues as extras, for he truly believed that was all they were worth.
The other students in Class 1-A took Bakugo's horrible behavior in stride. Each of them had enrolled in UA with a goal in mind, and it would take a lot more than an aggressive loudmouth to intimidate them. For the first time, Bakugo wasn't getting fawned over or given preferential treatment, instead being teased and made the butt of jokes. He was humbled over and over, such as when he was forced to use the full power of his Explosion Quirk to defeat Uraraka during the Sports Festival. When he was captured by the League of Villains, Bakugo was powerless to escape on his own and might have remained their prisoner had the team of Yaoyaorozu, Iida, Todoroki and Midoriya not intervened.
Realizing his classmates weren't pushovers was a tough but necessary pill for Bakugo to swallow. He was beginning to acknowledge them as equals -- another first for him in MHA -- and the worth they'd bring to him in actual hero work. Even though they didn't have all-powerful Quirks like he did, his classmates had abilities that could shine even brighter than his Stun Grenade, given the right opportunities.
Bakugo showed excellent leadership skills during his Joint Training match, both empowering his teammates with his bravado and suggesting tactical ways they could use their Quirks to overwhelm the enemy. It was a giant step for him, but the greatest indicator of his character development was his emotional and long-overdue apology to Deku for how horribly he'd treated him during their youth.
Bakugo's battle with Shigaraki Tomura has to be doubly satisfying for him. Apart from the opportunity to test his strength against the strongest villain ever, it provides the opportunity for him to finally pay Shigaraki back for the slight he made during the Paranormal Liberation War.
When Shigaraki encountered Bakugo, he immediately ignored him, stating that he had no further use for the hothead. The casual dismissal annoyed Bakugo to no end, especially because this was exactly how he used to treat others he felt were weaker than him; ever since then, he's been relishing the opportunity to fight Shigaraki once again.
Bakugo's fight against Shigaraki might end up being a highly gratifying moment for the young hero, but it's still far from being the final arc's main event. Being himself, he's going to put his all into the battle anyway, but even he understands that fact. His job at this stage is one of support, preventing Shigaraki from escaping his sky prison with the rest of the UA team long enough for Deku to get there. It's exactly the kind of role he would have ridiculed someone else for earlier in My Hero Academia, but Bakugo's newfound maturity helps him understand that this role is as important as any other.