Mr. Legend telling a young Kotetsu that he could be a hero too.
Wild Tiger telling Tony that he could be a hero too.
The entire second part with Wild Tiger and Tony which is a long Call Back to Kotetsu's childhood; telling him about how he went through the same experience, that his powers are meant to be used for good even though Tony thinks his are too "creepy" and "not cool like the other heroes'"; and later proving that by pretending that his power has run out while in the middle of saving someone to get Tony to use his powers to help at the last moment. It's an Establishing Character Moment Of Heartwarming for Kotetsu as a Friend to All Children, culminating in telling him the above, and as a Humble Hero when he also persuades Tony to turn himself in first even though he'll only get points if he arrests him instead.
Episode 3: Wild Tiger told Barnaby that he will not abandon his partner as the latter is trying to disarm the bomb. Barnaby smiled a bit.
Episode 4: Blue Rose ticked-off that Wild Tiger and Barnaby bet on whether or not that she would show, looks aside and smiled knowing that they were worried about her in their own way.
Episode 5: Barnaby scoffs at Tiger wishing him a happy birthday... but once his back is turned to Tiger the crook he's dragging away notices that he's smiling. Aww.
Kotetsu motivating Ivan to stop wallowing in his Heroic Self-Deprecation and Ivan's subsequent heroics, including standing between Lunatic and Edward.
Barnaby's flashbacks to Tiger being nice to him. And this is the first time we actually see a genuine smile from him.
Barnaby walking alongside Kotetsu's stretcher at the end. He's been dismissive and reluctant to work with Kotetsu up until now. Then Kotetsu, with his old-fashioned ideas about heroism, takes a superheated flame arrow for Barnaby. Barnaby is clearly shocked and moved by the act, and it becomes a turning point in their relationship.
Dragon Kid scorns the flowered hairclip that her parents gave her as much too girly...until she finds out what the flower is supposed to symbolize. After that she's never without it.
Barnaby tucking Pao Lin in.
Kotetsu and Barnaby's talking about Barnaby's parents.
Tiger insisting that Barnaby should ignore the current crisis and continue to the prison to confirm whether or not he's just found his parents' murderer, promising that he can handle things (and outright guilt-tripping him by accusing Barnaby of not trusting him when Barnaby continues to hesitate).
Barnaby's visible distress at hearing that Tiger is in trouble, and his subsequent decision to turn back, showing up just in the nick of time. Soon followed by the two of them standing back to back as they prepare to fend off the automatons.
Episode 12: When Wild Tiger's fight with Jake starts badly we see a civilian trying to get a taxi saying he doesn't trust in the heroes any more, he's flatly refused by Ben Jackson, Kotetsu's old boss, saying he won't take him because the guy just bad mouth his friend.
"Are you alright, Bunny?"
Tiger saying "I trust you to trust in me" to Barnaby and then Barnaby's face as he tries to stop himself from grinning.
Seeing Kotetsu finally getting some respect from the public is pretty heartwarming, as is the genuinely friendly dynamic (as opposed to the act they put on in early episodes) between Kotetsu and Barnaby.
Rock Bison catching a break near the end of the episode.
Episode 15: Sky High using the thought of Cis to destroy the psychotic robot, Cis.
Kotetsu's dream. All he wants is to impress his daughter and earn her respect. Quickly turns into a tear jerker when we realize he's losing his powers and feels like he'll never be able to achieve his dream without them.
Becomes doubly heartwarming at the very, very end of the series, when he finally gets his wish. And you can tell it's the proudest moment of his life.
Kotetsu coming to Kaede's rescue when she is trapped in a collapsing shrine during a thunderstorm. His Hundred Power runs out before he's finished lifting the fallen tree away from the entrance, but he still manages to lift and hurl it away by sheer force of Heroic Resolve.
Moments after it's shown that an Unflinching Walk can be both heart warming and badass.
Kaede's drawing of herself and Kotetsu, with Tomoe waving from heaven.
Episode 19: "There's one man I feel I can never measure up to, and my only wish is to become someone who's worthy of his trust."
Episode 20: When Kotetsu finds the ornamental pin he got for Barnaby in Maverick's office, him saying "I'm glad I didn't lose this. It's really important to me".
Kaede's absolute faith in her father's innocence despite knowing his faults well. Followed by her Grandmother revealing the fact that Wild Tiger is actually her dad.
Ten year old girl. Estranged relationship with her father. Still goes into Sternbild to save her dad. Alone. With her own piggy bank money.
And Ben coming to save him as well, where Ben reveals that no matter what, Tiger will always be his favourite hero and friend. He even has both of Kotetsu's trading cards (one in the blue Topmag suit and one in the green/white Apollon Media suit) on display in his taxi cab.
Kotetsu's basically having the worst day of his life. He's been framed for murder, wiped from the memory of all of his friends and coworkers, chased all over town, and berated by a hobo who doesn't want to share his spot. He looks up to see a news broadcast which tells him that not only has Barnaby probably forgotten him too, but he now has a personal vendetta against him for allegedly killing Samantha. Kotetsu's reaction to this news? Relief that Barnaby's safe.
"Our NEXT powers exist to protect the ones we love."
Blue Rose saying that she believes that Kotetsu is not someone who would kill.
Tiger telling Bison, shortly before his fight with Barnaby, "If anything happens to me, take care of Kaede."
Kotetsu hugging Barnaby after getting the latter to remember.
"You and I...we were the best team ever!"
"How dare you bring shame on Wild Tiger's name!?" Barnaby still remembers how important Kotetsu is to him, even if he can't remember it was him exactly.
"Take care, 'lil Bunny."
Blue Rose's speech.
Rock Bison debating pressing the switch on his collar. That in itself isn't a heartwarming moment, but his reason is. He wants to make sure that he'll be able to keep his promise to take care of Kaede if anything happens to Kotetsu.
Barnaby confessing that he's been practicing making fried rice hoping that Kotetsu will try it someday.
From beginning to the end, but especially the ending.
Especially the bit about how Mr. and Mrs. Brooks came up with the deactivation code for those mecha.
"Kaede thinks her daddy's cool! That's the most important thing to me!"
"If you're making a comeback, I suppose I'll have to as well." "Why's that?" "Because I'm your partner!"
Blink and you'll miss it, but Tony, the NEXT from way back in Episode 2, is shown briefly hanging out with the star figure skater.
One of the NEXT criminals the heroes contend with puts Fire Emblem into a coma, with him being forced to live through a nightmare where he is mocked and bullied for being gender-queer. When Blue Rose and Dragon Kid go to fight the NEXT that attacked Fire Emblem, when the criminal mocks him as well, Dragon Kid retorts that in all her life, she had never met anyone else like Fire Emblem who was as strong as a man, yet as caring as a woman. Fire Emblem overhears her from a monitor in his hospital room and reawakens from his coma to aid her.
Pretty much the entirety of Sternbild encouraging Kotetsu to return to the First League as Barnaby's partner. Kotetsu spent the first half of the movie feeling worthless and unwanted, and then he has whole crowds of people cheering him on. Before making his decision, however, he asks Barnaby if he's okay with it. Barnaby grins and says he's fine with it, albeit with some sarcasm, so Kotetsu flashes the thumbs up to the crowd. And then Barnaby does the same, bumping Kotetsu's fist with his in a very familiar gesture.
While Kotetsu thinks he's doing Barnaby a favor by not fighting his new boss's decision to promote Barnaby and leave him behind, we see Barnaby acting very much like Kotetsu throughout the whole movie - putting most of his salary towards helping out an orphanage, encouraging his new partner to focus less on points and more on helping people... Barnaby holds Kotetsu in very high esteem, even if they do still bicker, and their relationship has come a long, long way from the beginning of the series.