There's a whole series of these moments in Pluto, though they verge heavily on the Tear Jerker department:
Atom, somehow reawakened by the hatred in Gesicht's memories, moves in for the kill on Pluto. However, before he can strike, there's a flashback to Gesicht's death. When Gesicht is shot he feels no hatred; instead he falls to his knees, smiles and says "Nothing will come of this. Nothing will come of hatred," before dying. Atom realises that Gesicht wanted nothing to do with hatred so he spares Pluto at the last second.
In the next flashback we finally discover the meaning of "500 Zeus a body.'' Gesicht rescues a human boy from the clutches of a criminal on top of scrap-heap and then sees the boy's family reunite; saying they're 'keeping him with us til' the end of the world'. Later, right before leaving, Gesicht spots a still-alive robot child in a pile of rubbish. The scrap-heap owner wants to use the child for parts but Gesicht is taken in when the boy clutches his arm; so he buys the boy for 500 Zeus. The flashback ends with Gesicht holding his new son promising that he'll keep him with us til' the end of the world'. Even the tragic events that followed can't detract from this moment.
Uran's returning to meet the "wandering soul" Pluto, finding that he's finished his painting.
Uran: Mister...This brings tears to my eyes. I'm sorry I called you a bad artist. This is what you were born to do! You can make the whole world bloom like this picture!
Any scene with Epsilon and his adopted children, but especially when Wassily goes to say goodbye.
Epsilon: Wassily, you...you said my name for the first time!