Tintin In Tibet. Chang goes through a real Trauma Conga Line, having survived a plane crash with injuries. Then a Yeti takes him and while Chang thinks the Yeti's going to eat him, the Yeti actually brings him food so he'll get his strength back up. Then later in the story, he reveals that the Yeti picked him up and took him away from the previous cave because Tintin was coming to the crash site. The Yeti did this because he was afraid that Tintin and co was coming to harm Chang, so the Yeti was actually trying to protect Chang. After Chang is rescued and finally being taken to where he can receive medical attention, the Yeti's sad cries are heard (and by the characters as well!) because of the loss of the yeti's only friend. It ended well; but had they been unable to save Chang, he probably would have died in the mountains because the Yeti didn't know Chang really needed medical attention even though he had saved Chang's life. It also doubles as a Tear Jerker.
Another extremely heartwarming incident in the same story: Captain Haddock attempts to sacrifice himself by cutting his lifeline in order to save Tintin, who is tied to the other end and unable to pull Haddock up. If there was any doubt that Haddock is a heroic and loyal friend despite his vices, this scene obliterates it.
Tharkey coming back to rescue them should count as well.
Haddock repeatedly comes back after swearing up and down that Tintin was crazy for going off on his hare-brained rescue mission. The first time he surprises Tintin by recruiting an experienced Sherpa guide and several porters (and a rucksack full of whiskey), and the second time he shows up at a remote village, sheepishly explaining that he's only there to get a photo of the Yeti to sell to a magazine.
Also a Real Life Heartwarming Moment: Herge had used a friend he made while researching for The Blue Lotus, Zhang Chongren, as the basis for Chang Chong-Chen, a friend Tintin makes when he is in China. By the time Hergé wrote Tintin in Tibet, he had not seen Zhang for several decades, but the French media managed to find him and arranged a trip for him to travel to France, where the two friends finally met. There is a photo of the two of them sitting in front of a cutout of Tintin and Chang saying the words used in their reunion in that comic.
Tintin/Hergé: I Knew I'd find you in the end!... This is wonderful!"
Chang/Zhang: "Tintin! Oh, how often I've thought of you!"
The Black Island has a Gorilla who's sent to kill Tintin. It's injured and Tintin saves the animal, who then proceeds to become his friend.
The end of The Blue Lotus where Chang is adopted after having helped stopped Rastapopolous.
Wolff's Heroic Sacrifice in Explorers On the Moon. Especially in the Nelvana adaptation wherein Captain Haddock yells at the Thompson and Thomson duo not to say anything bad about Wolff.
Tintin hugging Haddock in "Tintin In Tibet" for being a great friend.
Haddock's motivational speech to Tintin during his Heroic BSOD stage:
Captain Haddock: I thought you were an optimist.
Tintin: You were wrong, weren’t you? I’m a realist.
Captain Haddock: Ah, it’s just another name for a quitter.
Tintin: You can call me what you like. Don’t you get it? We failed.
Captain Haddock: Failed. There are plenty of others willing to call you a failure. A fool. A loser. A hopeless souse. Don’t you ever say it of yourself. You send out the wrong signal, that is what people pick up. Don’t you understand? You care about something, you fight for it. You hit a wall, you push through it. There’s something you need to know about failure, Tintin. You can never let it defeat you.
What makes it even sweeter is that after the intro credits, he's the first person you see in the film.
After the chase in Morocco, Tintin is wrestling Sahkarine's bird for the last scroll. Sahkarine threatens to drown Haddock if Tintin doesn't let the bird go. Sahkarine drops Haddock into the water, and Tintin goes after him instead of getting the scrolls first. Aww.
This one's more heartwarming after a trip to the fridge. During the scene where Haddock has a flashback to Sir Francis fighting off pirates on the Unicorn, Sir Francis lights the magazine to blow the ship up. Haddock, thinking he is Sir Francis on the ship, grabs Tintin and tosses him out the window so that he's not killed when the "ship" blows up. Here's the heartwarming part: Sir Francis was by himself and only had enemies around, so logically Haddock should have just jumped from the window himself and left all the "Pirates" behind. Even in the middle of a hallucination or a flashback to a previous life Haddock still has the presence of mind to make sure his friend was safe.