Just about any scene between Almaz and Sapphire in Disgaea 3.
Really shown during the Vita version's Side-Story "Battle for the Test", where Sapphire wants to reclaim her test before the results are posted. The reason why? She doodled herself and Almaz beneath a Heart on her test sheet, and didn't want anyone else to see it.
Any scene concerning Mao and Raspberyl's rivalry, especially in Raspberyl Mode where it really takes center stage. Of particular note is episode 3. Raspberyl storms Celestia in order to acquire the "Heart of an Angel" and become the Ultimate Delinquent. Then she forces a meeting with the Archangel, who turns out to be a promoted Flonne. Flonne demands to know why Beryl really did this, and Raspberyl grudgingly admits that really she's doing it all for Mao: their rivalry has always been what has driven him to greatness, by making him desire to one-up Beryl by becoming the Ultimate Honor Student. Everything Raspberyl has done, all the hard work and volunteering, was to inspire her friend. Flonne tells her she doesn't need the Heart of an Angel, she already has one.
The scene where Almaz gets his hero title back. It's touching to finally hear how deeply grateful Mao actually is on the inside for everything he'd done for him.
The ending of the Vita release Side-Story "Legend of the Super Delinquent". Asuka and Kyoko have been noticing Beryl acting strange, so they follow her to figure out why. She stayed up for 10 straight days hand-crafting dolls of Asuka and Kyoko as a present to celebrate their group having been formed 100 years ago. Also detailed is how they met; Beryl donated bone marrow to treat Asuka's Demon-cell Leukemia, and rescued Kyoko from several demons holding her for ransom.
The Death Institute, Majin Academy ending. Even though Rutile was basically used by Stella to steal the Dean's certificate to Evil Academy, and even bascially treated like shit, she's still willing to reconcile with Stella and try to help her school.