What about the death of Master Asia? After a very last, gruelling battle, Domon tops his Master out, only to find out that he wasn't really as much as an SOB that he thought he was, he was misguided by his mistake to be absorbed in Gundam Fights that ravaged the Planet Earth and that everyone only cared about the Fights, not the planet. And then, Master reveals that he still retained his honor, not infecting himself with the DG Cells. Finally, for one last time, master and disciple recite the motto of School of Touhou Fuhai (Look, the East is burning REEEEDDD!!!), and Master Asia finally perishes after finishing the reciting, followed with a very crushing cry of Domon... "SHISHOOOOOOOOO!!!!!!"
The worst part is right as Domon is about perform the Erupting God Sekiha Tenkyoken. If you look closely, you can see what look like tears forming in the God Gundam's eyes.
And if that wasn't enough, the somber reprise of the Shining Finger theme that plays really hammers it home. Domon shaking, trying to hold back the tears as he prepares to do the deed while giving his final goodbye to his brother just before this begins is equally gut-wrenching. The whole sequence is so tearjerking that even Stalker is visibly trying his damnedest trying not to break down in tears while recapping the event the very next episode.
Also the very final episode is... depending on the viewer's opinion either a TearJerker or a hilarious scene. At the very least it is very impressive, when Domon saves Rain and they use the Love-Love Sekiha Tenkyoken together
The final moments of Master Asia in G Gundam. The Kyoji moment may have help build it up. It only becomes even more poignant if you understand the true meaning of the word "shishou". Apparently, it doesn't just mean "master" but refers to someone's first teacher, who they hold in very high regard for life no matter how far they advance, even if they transcend their master utterly. Thus adding another layer to Master Asia's surprise when he says to Domon: "after all this you still call me master?"
And when Rain decides to leave after learning the truth about the Devil Gundam and thinking that, since her dad was involved in the whole fuck-up, she can't face Domon anymore? Seeing Domon try to desperately reach for her, only to fail, is heartbreaking.
A minor one, but deserves mention here: during Allenby and Rain's Designated Girl Fight, a Brainwashed and Crazy Allenby is rampaging and looking for Domon. To see the lonely and frightened side of her come completely to the forefront, frantically searching for the only one who can understand her can be heartrending. Her Anguished Declaration of Love may be the clincher.
Theh, in final episode, when Allenby makes Domon realize ne heeds to confess his love to Rain and few episodes earlier, when she mentions she knows how to Domon Rain is most important person in the world - when you think about it, for somebody who had life like her and went through what she just did realizing the only person who understands her and man she loves will never return her feelings because he belongs to another must have hit pretty hard.
The episode where Domon upgrades to the God Gundam - Rain remotely controls the nearly-totaled Shining Gundam to get Domon's battle data to the God Gundam. The scene is both heartwarming and sad, as Domon had been fighting alongside the Shining Gundam for almost a year...