The final scene
I'm not sure I've ever been moved as much by the end of a film, not in a long time. I remember thinking as the film was winding down, please show us what he becomes, please show us him dancing as an adult.
We see his family there and Micheal, the music is amazing, and then we see a full grown Billy looking simply magnificent as the lead swan, preparing and even seeming a little nervous, he smiles when he's told his family is there, then the gasp of his father as he bursts out powerfully onto that stage. It was honestly too much. Overwhelming. So beautiful. Perfect.
Till the gossamer thread you fling, catch somewhere, O my Soul.