Derek's single minded determination to get Odette back even when everyone else has given up on her. "Everlasting love" indeed.
It's kinda sappy but...
Odette: Will you love me, Derek, until the day I die?
Derek: No. Much longer, Odette. Much longer.
When Derek finds Odette after searching for her for most of the movie. Remember, the last time they saw each other was when Odette turned down Derek (after spending most of their childhood bickering). There is no argument, no harsh words, nothing but Odette simply saying "Hello, Derek" and Derek runs to her as the music swells.