Swan Lake

There are also versions of the libretto with a sad but unending death.

An excerpt from the article 14 facts about Swan Lake

As an example, there is the 2006 New York City Ballet version, in which Siegfried’s betrayal condemns Odetta to spend the rest of her life as a swan. The lovers do not reunite in the act of death but are separated forever, as the Swan Queen sails away, and the prince stays behind.