The opening narration from Jake and the interactions between him and his family during it. This includes, but is not limited to.
Jake and Neytiri celebrating the birth of Neteyam, their first son.
Jake teaching Neteyam how to fish using a bow.
Jake and Neytiri wholeheartedly adopting Kiri as one of their own, even despite her mysterious origins.
Jake and Neytiri having the Na’vi equivalent of a date night: flying on their Ikran together while the kids are at home.
And finally, a family photo of all the Sully family, with camera-flashed eyes and all.
The humans who stayed behind on Pandora are accepted as honorary family members, allowed to participate in holy events like they were Na’vi themselves.
The relationship between Jake, Neytiri, and their kids is adorable, especially when they’re little babies like in the beginning narration/flashback.
Kiri’s adopted siblings show absolutely no hesitation in defending her from the more xenophobic members of the Metkayina, with Lo'ak even starting a fistfight with Aonung, the son of the chief. And, as hardassed as Jake has become toward his kids and fitting in the tribe, he makes sure with Neteyam that Aonung and his group walked away from the fight on the worse side compared to Neteyam and his brother.
When Lo'ak walked off when he was unable to convince Tonowari nor his father Jake with regards to the truth about Payakan's outcast nature, Tsireya followed him and was willing to listen to Lo'ak's retelling of what happened to Payakan's entire family. When he was adamant that no one understands him and only sees him as an outcast, Tsireya simply reached out to hold his hand in hers and said, "I see you" which meant that she believed Lo'ak completely and wholeheartedly supports him.
Though it ends in a frustrating and nightmarish manner where she has a seizure while underwater before she can learn anything useful, Kiri's meeting with Grace's spirit is nothing but this where the scientist is nothing but loving towards her Na'vi daughter in the short time they have together.
The return of the Tulkun to the Metkayina village is truly a heartwarming sight, as the Na'vi come out to greet their spiritual brothers and sisters after so long. Special highlights include the baby Metkayina swimming to greet the Tulkun for the very first time, Tsireya telling her Tulkun sister how she "met a boy" (most likely referring to Lo'ak), and Ronal and her sister congratulating each other on their children.
Jake and Lo'ak have had a rough relationship for most of the film, with Jake getting frustrated at his son and Lo'ak feeling he's a constant disappointment to his father. Then in the climax, Lo'ak tracks down his injured father in the sinking ship and refuses to abandon him, instead talking him through slowing his heart-rate and staying calm so he can hold his breath long enough to swim out. Lo'ak assures Jake he believes he can do it, and helps him get to the surface with help from Payakan. As they're recovering, Jake turns to Lo'ak and simply says "I see you, son", with them finally reaching a mutual understanding.
Even terrorized and tortured by Quaritch and his squad, rightly fearing for their lives, the people of the Metkayina's neighboring tribes declare over and over again that they have no idea where Jake and his family are. Then Tonowari reveals to Jake that they were lying, at his behest. That's solidarity.
Jake and Neytiri's kids show nothing but love and care towards Spider, and treat him as if he were a part of the family and as another sibling: Neteyam and Lo'ak lightheartedly argue and tease with him the way that brothers do and he's shown to have a very close relationship with Kiri, with them constantly looking out for each other.
When Spider essentially gets captured by Quaritch and sent back to the base, Kiri begs Neytiri not to leave him behind.
Neteyam and Lo'ak do not hesitate to go rescue Spider while they're on the boat even though they've already rescued Tuk, Kiri, and Tsireya at this point and it'll only cause them more trouble.
After Neytiri nearly kills Spider in order to force Quaritch to release Kiri, Kiri and the others immediately rush up to Spider to make sure he's alright.
While Jake compares Spider to a stray cat that is always around whether you want him there or not, it's clear that he is fond of the boy even if he doesn't consider him family until the end.
While Quaritch says he does not consider Spider as his son due to the both of them being biologically different, his actions speak otherwise and Quaritch ultimately gave up an advantage when his son was held hostage by Neytiri. Spider would in turn return the favour and save him from a watery grave moments later.
After Neteyam's funeral, Jake tells Tonowari that he and his family will leave the Metkayina and return home, but Tonowari tells him that their family is now one of them and offers to let them stay with the clan, a proposition that Jake accepts.
Doubles as a Tear Jerker: what we see of the Na’vi afterlife (Eywa’s realm) is open to interpretation. When linked to spirit trees, do the living just replay happy memories of their lost loved ones based on knowledge they already have of them? Or do the souls of the deceased actually exist in specific moments in time forever? If it’s the latter, then the implication is that the dead get to stay within a personal “happy place” (at least those who were given a formal “burial” at a spirit tree location).
Grace’s afterlife shows her peacefully doing her lab work and as her Na’vi avatar doing field research.
The mere fact that Grace, who was so beloved by the Na'vi (and the fanbase), lives on through her daughter and is able to communicate with her through Eywa, telling Kiri how much she loves her.
Despite the rocky start to how Quaritch tames his ikran (by running up to it and punching it in the face), the creature does seem to form a genuine bond with it’s abrasive rider, since it turns out to have been hanging around the area of the movies Final Battle for what was likely hours after getting injured and separated from him, given how fast it flies to his side once he’s out in the open.
The end credits song, "Nothing is Lost (You Give Me Strength)" by The Weeknd, is this in a bittersweet way, considering that its lyrics pretty much reflected the feelings of the Sully family, particularly Jake and Neytiri, towards Neteyam's death. Even though they are mournful for losing him despite doing everything they can to protect him, they are still hopeful that one day they can meet each other again in the world beyond, and they'll dedicate the rest of their lives defending those they love, their resolve strengthened by the bond they shared with their fallen loved one that transcends life and death.
Been living this life so patient
Until I see you again, it's war we're facing
I know that if I die, my only choice is still defending
◊; you'd have to have a heart of stone to not feel anything regarding the wholesomeness on display!
