Saving an Archfiend. The Narrarator will even comment on how good he feels for doing so at times. It just feels nice to help save the world instead of destroying it further.
Also, seeing them come to you and offer their aid, particularly if it's one who was a total asshole in life.
The ending of "The Wicked Sorcerer". "If everyone was rich, there'd be no monsters".
The ending of "Child of a Monster". It turns out that Radux's Kobold mother attacked him (forcing him to kill her) not because she always hated him for being human, but because she knew that, as a Sorcerer, Radux would eventually be forced to hunt monsters, and so allowed him to kill her so he would be able to function in Avalon. Upon realizing that his mother truly did love him, to the point she was willing to die so he could have a better life, Radux is able to find peace and at least somewhat absolve himself of his guilt. The final image of the questline is of the Kobold transforming into a tree (as Kobolds do upon death) with a bright light shining down on it.
The lore for the "Noah's Desert" area. A trader, lost in the desert and dying of starvation, chooses to let himself die rather than kill and eat his loyal pet camel. Even when the chalice appears before him and offers him a way to cross the desert in exchange for his camel, he refuses (one of the very rare cases of someone declining the chalice's offer). It is the camel who chooses to sacrifice himself, turning his own body into a ship in order to save his master. The camel then spends the rest of his life tirelessly helping his master cross the desert trade route, even when the cargo he is carrying is too much to bear, motivated purely by loyalty.
A bit of a Meta example, but the community, especially in the Delta version. Join any random squad, and chances are the very first thing you'll see is a group of complete strangers telling you how pleasant it is to meet you. Not to mention if you go down, there's always at least one person who will drop everything to revive your character, even if it puts themselves in danger.