a lone wolf
A lone wolf is someone who left a group to be stronger, but now just sits around and stares at the ceiling like it's the most interesting thing in the world.
He left his group to be cool, but now he just stares at the ceiling and eats cereal for dinner.
She left her friends to be awesome, but now she just sits in the park and eats chips like it's her full-time job.
He left the team to be a legend, but now he just sits in his room and watches YouTube like it's a religion.