After the first mission in 1st's OCU campaign, every time Karen is mentioned (by anyone at all) is a moment of heartwarming to some degree.
In 1st: At the ending of Roid's story, Frederick publishes a book to disclose details of the unethical experiments the OCU and USN were doing during the Second Huffman Conflict. Then there come international outcries from people all around the globe, who demand to know the truth. This exerts enough political pressure on the supernations to make them admit that some of the information in Frederick's book is real. It makes one feel that at least some justice has been done for Karen and all the people who were killed in the war, or worse.
This troper also likes the ending of the USN campaign of 1st. Having put Winger to justice, Kevin decides to join USN peacekeeping forces, doing what he can to protect children in the politically unstable South American states from suffering the same fate as Maria did. And he keeps a photo of Maria in his wanzer's cockpit to remind himself of that. Furthermore, if you have played 4, you would know that Maria has been working in Venezuela, and may well be operating around South America. It really makes one wonder if the two may, by some chance, meet again one day.
The ending of 2 is pretty great, too. After decades of exploitation by the OCU, Alordeshis finally gain the independence they want. Sure, as revealed in 5, economically, this may not be the best idea, but hey, seeing that the OCU was treating Alordeshis as test subjects for the FENRIR, this troper couldn't help but find the ending uplifting.
At the end of 4, we have this: In the last minute before the transport plane takes off from Cumana, Darril decides to give half of Diaz's gold to Luis, so that the latter can use the money to rebuild his home country. This really nails down the fact that beneath his facade of a somewhat selfish and deceptive jerk, Darril is still a decent guy after all, as lampshaded by Renges and Chaeffer.
The entire epilogue of 5 is pretty much made of heartwarming. We watch an aged Walter talks to Lynn's gravestone lovingly, showing that while their relationship had its challenges, they really did care about each other after the hardships they have experienced together.
And then a young woman runs up excitedly to greet Walter (whom she refers to as 'father'), telling him she's finished pilot training and is being assigned to his base. We are given a close shot at the young woman's face. She resembles Lynn a lot...
Just before the credits, Walter and Glen reconcile in Alaska. After decades of being treated as a puppet by Morgan, Glen finally regains his memories and has a nice, warm exchange with his old childhood friend, before MIDAS vaporizes him. Oh, when the reactor complex begins to fall apart and Walter runs for his life, the ceiling collapses, and a particularly large piece of debris is about to crush Walter... only for Glen's wanzer to save him by suddenly throwing itself between Walter and the debris. A couple of scenes later, having Outrun the Fireball, Walter and Lynn stand outside the complex to watch the aurora created by MIDAS's radiation. As if to top it off, Lynn then muses about how Glen's wanzer can move with its pilot dead, finished with her recognizing that humans are more than mere substances.
Much of Evolved's story is rather narmy, but when Dylan tells Adela that he would share her grief over her past, many players' emotions are indeed stirred.