Koichi re-discovering his ability to push himself through the air just long enough to save himself and Makoto from a lethal fall.
All of the battle between Knuckle Duster and Kuin. He's just a quirkless brawler, but his training and ability to see through Kuin's tricks give him the edge he needs to repeatedly knock the smug out of her, even driving her to flee in fear while he gives chase at one point. To finally end it, Knuckle Duster delivers a taser blow to stop Kuin's heart (keeping in mind his daughter Tamao's body is being used as the host) which causes the swarm to instinctively flee, allowing him to pull out the queen bee. Then he reveals his taser has a defibrillator function that he had used to save his own life earlier, and starts using it to bring back Tamao.
Koichi discovering his ability to truly stick to vertical surfaces. He truly becomes The Crawler as he achieves this.
Koichi's experimentation with his Quirk causes him to discover that he could use and fire a light repulsion out from one of his limbs.
Knuckle Duster's return to the series in chapter 44, where we find that not only is he still tracking down the supply of Trigger on his own, he was also once the pro hero O'clock, but kept fighting as a Badass Normal vigilante after his quirk was stolen.
Chapter 51: Koichi shows up between a severely bruised up and wounded Captain Celebrity and Kemikaze, a Next-Tier Villain and regenerating suicide-bomber with exploding fists, in order to stop the latter from blowing the former up who's holding up the tower a number of civilians and pro-heroes are present in. Sure, his hand-blasts are nothing but a mere peashooter against the villain, but it's still enough to force it to reload its explosions and stall for time for as long as possible. This despite knowing that if Kemikaze gets close enough to punch him even once, he'll be a goner.
In chapter 54, in spite of all the heroes' efforts, the Sky Egg is falling down, dooming 50,000 people... Then Tsukauchi calls All Might. The Sky Egg is landed safely, everyone and every stray that could have been flattened by the Sky Egg is removed, and some onlookers get a picture of All Might posing for them.
Unwilling to give up, Six has the remains of the suicide bomber monsters fuse with each others to create the Cluster Bomber, that immediately dies generating two hundred monsters-enough that, according to Six, the heroes can take down only half before the others slaughter the people there. The heroes react in shock and horror... Then All Might uses the Nebraska Smash and the kamikaze drones are sucked in a tornado that smashes them on each other, destroying them without injurying anyone.
Chapter 64: After all the other heroes nearby were knocked out of commission by Garvey, a huge villain that can use any power he absorbs, Aizawa is forced to face off against him alone. Using his own Quirk and agility to avoid getting blasted by the powers Garvey had absorbed to that point, he feels helpless to actually finish the fight because the villain is so much larger and stronger. When he hears his friend Shirakumo encouraging him, though, Aizawa rallies himself and figures out a way to use his capture tape to hit Garvey with his own attacks. It veers into Tearjerker territory afterward, though, when it turned out that the speaker Aizawa thought he heard his friend's voice through was broken, and Shirakumo was dead all along from one of the earlier attacks. Hearing Shirakumo's voice was just a trick of his own mind.
Chapter 83: When faced with Endeavor blowing up the street beneath him and Six on his back Koichi one-ups his Double Jump by applying the same mechanic he does for his hand blasts to his feet. The end result? Full-on Flight as he rockets himself and Pop into the air.
Chapter 107: The Crawler's fight with No.6 reaches a point that 6's hallucination of O'Clock concludes that, for 6, Crawler is as big a threat as All Might and is someone that 6 can only run from.
With the later reveal that this is All For One projecting himself into 6's mind to provide guidance, this is arguably more awesome. The greatest villain of the Hero Aca world considers Koichi on par with his arch-nemesis.
Chapter 110: The triumphant return of Knuckleduster to interrupt No.6 attempting to snipe Crawler with a supersonic rifle round. How did he make it in time? How did he know where No.6 would be? Because sniping was one of his favorite tactics as O'Clock.
Chapter 120: Koichi's and 6's battle reaches a level unforeseen in the series: A telekinetic strong enough to fly through the air and punch through walls VS an immortal giant made of living plasma.
The final chapter shows Koichi finally becoming a pro hero, with a more fitting title of "The Skycrawler". He's sent to save a malfunctioning airplane from crashing, showing how far he's come from the guy who could only scoot around slowly with his Quirk.
