Losing in the love triangle, but winning the film?
I can't imagine any leading actors or actresses who would be happy to be the third wheel in a film's love triangle. But if you've got it to do, it could hardly be better handled than Eleanor Parker in Scaramouche.
She may have lost Andre, but for my part (and I seem to find general agreement with me from the limited feedback I've seen over the Leigh/Parker question) I don't leave the film thinking about Janet Leigh's Aline, I'm thinking about Parker's Lenore and wondering what in the world Andre was thinking.
And that is how you win the film. Well played, Eleanor Parker.