He is very close to earning his final badge, the "Assistant Senior Wilderness Explorer" badge, which he's been working towards throughout the movie. However, in the end, he decides to stay with Carl, the old man he's become friends with, rather than returning home to earn the badge. He recognizes the importance of their friendship and chooses that over his ambition to become a Senior Wilderness Explorer.
It's a powerful moment that shows Russell's growth and understanding of what truly matters.