Heartwarming / Deku? I think he's some pro...

• The underground heroes pretty much adopting Izuku as one of their own, and showing the validation he's never found. They also get furious when they learn everything he has suffered because of his Quirkless status, and recommend him en masse to join U.A.'s Hero Course.
• Conversely, Izuku not only gaining friends, but also acceptance - the heroes don't care that he's Quirkless, clearly respect him and they also help him achieve his dream of becoming a hero by training him up to standards.
• After learning the truth about One for All, Izuku gets furious because Mirio, who already had a powerful Quirk, got an even more powerful second Quirk on top of it, while he remains Quirkless. However, when Sir Nighteye implies the possibility of Izuku getting One for All, he decides not to accept, because he wants to inspire Quirkless kids in the future by showing them they can be heroes, as well.
• Aizawa consoling Izuku when he has a panic attack.
• Izuku finally finding friends of his age when he joins U.A. Much like the Pros, most of them don't care about his Quirklessness beyond the handicap it may cause him in the course.
• After the Battle Training fight, Izuku could have easily asked for Bakugo's expulsion (which Aizawa was clearly willing to grant), but instead asks Aizawa to give Bakugo a second chance, because he knows that Bakugo can be a good hero if he is given the chance to unlearn his nastier behavior.
• Even though he lost in their fight, Izuku is not upset with Shinso, and in fact tells him his Quirk is perfect for heroics. For Shinso, it is probably the first time someone has outright reaffirmed he has a great Quirk for being a Hero.
• After her match with Bakugo, Izuku consoles Ochako, giving her a hug and telling her that she was awesome in that fight.
• The progress Bakugou shows in his therapy sessions with Hound Dog:
  • During the awards ceremony, instead of having to be chained and muzzled in anger over the result of the finals, he instead just takes the medal but refuses to wear it. Getting his point across in a much more subtle and heroic fashion.
  • Then, when considering who to intern with, he doesn't pick the highest ranked hero (Best Jeanist), but instead goes for Mirko, who actually compliments his new style and can teach him how to become Reformed, but Not Tamed.
  • Mirko is the one that finally gives him the final push towards his new outlook: she points out that strength is not about being the strongest, but about being strong enough to save those in danger.
• When Izuku is recognized in the train a few days after the Sports Festival, he gets some recognition that gets washed down when he confirms he's Quirkless, with an old man even saying that he should die so someone with a Quirk can replace him. Fortunately, when he drops off, a woman comes up to him, apologizes for not saying anything and tells him that her daughter is Quirkless as well and has found inspiration in Izuku for being able to compete with people with Quirks. And when she asks for an autograph, Izuku tells the girl in the note that she, too, can prove that Quirkless does not mean worthless. Only a couple of months as a trainee hero, and he's already doing what he told Sir Nighteye.
• After the Sports Festival, Izuku easily befriends Shinso when he joins the Hero Course and shows no worries about being potentially brainwashed. He also grins and gives his full support to Shinso as he comes up with his hero name.
  • Also, Shinso getting three internship offers, when he was previously in the General Course. In the end, he picks Aizawa, his favorite hero.
• At the end of Chapter 48, Aizawa does something he would have never done if it hadn't been for Deku: he calls Emi to ask her for a date.
  • The two have a great day together, with Aizawa taking her to the cat cafe of a couple of former criminals he helped go legal (from My Hero Academia: Vigilantes), and (after catching a pair of thieves) ending with a Big Damn Kiss.
• Shouto went to see his mother after the festival, because he wanted to ask her if he could use his fire Quirk without being like his father. His mother tells him that yes, he can be a hero and kind at the same time.
• Izuku's pre-UA work has the unintended consequence of giving Toga Himiko the chance to avoid becoming a villain thanks to Vlad King finding and adopting her.
• Even though they're villains, the League recognizes how messed up it was for All for One to force a Quirk onto a child and stand by Shigaraki.
• When Toga gets Kurogiri's blood, the fight is essentially over. One of the first things she does? Get Izuku back to U.A., to be checked over by Recovery Girl as he falls asleep in Uraraka's embrace.
• Class 1-A wants to make sure that Izuku will be properly praised for his role in ending the League of Villains rather be seen as a weak victim, so they collaborate with Nedzu and send Aoyama to "leak" everything Izuku did to a journalist that will report the truth.