In the finale of G Gundam, when Domon's girlfriend Rain had been captured and brainwashed by the Devil Gundam, Allenby pulls an I Want My Beloved to Be Happy, and tells Domon "Go after her. Or I'll never fall in love with anyone else Domon, but you," He then breaks into a heartwarming speech to Rain, telling her that he never blamed her for his troubles, and that their year together was more than just the two of them working together. He then finally gets to tell her exactly how he feels about her. It has to be seen to be believed.
Don't forget Domon's reunion with his Disappeared Dad, or more exactly, his recently defrosted dad. Dr. Kasshu explains to him what has been going on with the newly evolved Devil Gundam and what he has to do to stop it and save Rain, but right before Domon leaves, Raizou stops and tells Domon "You've grown, my son. I'm So Proud of You". Domon then smiles and thanks his dad, promising to return before taking off.
Just before his final match with Domon, Sai Saici finds a letter that makes him stop goofing off and put everything into his training, to the confusion of his guardians. Turns out the letter was from his late father, lamenting his inability to restore the Shaolin Temple and asking Suisen and Keiun to raise Sai Saici. Sai Saici risks death so that the Emperor will grant his request to restore the temple and fulfill his father's dream.
One more for the finale; by the end of the series, each member of the Shuffle Alliance is seen with together with the persons they love and care for the most as well: Chibodee is with his Four-Girl Ensemble, George is with Maria and Raymond, Sai is with Keiun and Suizen (snd a bonus photo of Cecile), and Argo is with Natasha..
Chibodee's girl group singing to him to help him get over his crippling fear of clowns while fighting the Jester Gundam. It makes him realize that they've become his new family since he lost his mother, and that he's no longer alone.
The entire final battle with Master Asia. Domon finally realizes how badly Master Asia is hurting and that he isn't a Complete Monster after all, even if his actions are wrong, and spends the fight trying to convince Master Asia to stop. When Domon lands his Finishing Move, Master Asia congratulates him on being a worthy successor. As he dies in Domon's arms, he finally apologizes for his misguided actions and reconciles with his student, and passes away after a final cry of "Look! The East is burning red!" Many Manly Tears have been shed because of this, but it doesn't stop being touching.
Adding up to the heartwarmer is that while apologizing, Master Asia opens his shirt and revealed his bare chest, clean and no traces of Devil Gundam Cells at all, meaning that he never stooped that low like certain others, he's still a honorable fighter throughout his life despite his misguided actions.
God Gundam when it is first used. The dramatic scene, how God Gundam holds Shining Gundam like a dead princess, Rain telling Domon to go to Hong Kong, it seems more like the gundams are people than mechas. Especially the tearjerking, "Good bye, Shining Gundam.".
And then we have the end of the episode that comes after this. Domon manages to arrive to Hong Kong despite being attacked by Master Asia (and saved by Schwarz) as well as by then nameless mobile suits -- with one second to spare. Rain, who has been worried sick for Domon and unable to help him further, runs to the dude and goes Tsundere, calling him an idiot and then sobbing against his chest. Domon then tells her "I'm sorry for making you wait, Rain" in an unusually tender voice, and as they look into each others's eyes, fireworks go off on the background.