I felt that feeling in avengers endgame movie, I was sad about retiring Avengers but satisfied about good things happened in the way
I think "bittersweet" fits. Merriam-Webster: "pleasure accompanied by suffering or regret" https://www.merriam-webster.com/dictionary/bittersweet
a silver lining TFD n.
a comforting or hopeful aspect of an otherwise desperate or unhappy situation
I felt that feeling in Avengers Endgame movie: I was sad about retiring them. But the silver lining was the satisfaction about the good things that happened.