Kirk and Edith Keeler. She was his Kobyashi Maru -- the no-win scenario. He was in love with her, but had to let her die to save a universe.
Agreed. She was in the Depression, but she had a sense of the positive things to come. How could Kirk not fall for that sort of optimism (when he knew that it was right)? And then to have to watch it die...
Gets my vote.