The final moments of The 2nd Runner. After stopping Aumaan from destroying the Solar System, Dingo and Leo returns to Ken (on board the fake Anubis) from Phobos' explosion with their mechs completely wrecked. Dingo and Ken immediately rushes and embraced each other with their frames. In the anime cutscene that followed, Ken cries into Dingo's chest when he said her father was secondhand (or so the translators this assembled the dialogue together).
ADA and Leo bonding in the second half of the first game especially during their trip to the Central Hub. From Leo telling ADA a story of his childhood as a means of explaining his reasons for continuing to work for BRAHAM in spite of his repeated stated reluctance to do so to Ada telling Leo not to be careless in action as not only does she need him but she does not want him to die. Leo expresses nothing but lament and sadness when he learns that Jehuty is to self-destruct as part of its mission to Mars, destroying ADA as well. The two had really come far in their relationship since the beginning of the game.
The second game took this even further. Leo was willing to go againts order to protect Jehuty and ADA, and ADA retained a lot of Leo's words, like suggesting Geyser on the UNSF LEVs when Dingo wanted to save the civilians.