I can't stand burnt toast. I loathe bus stations. Terrible places, full of lost luggage and lost souls. ... And then there's unrequited love. And tyranny. And cruelty.
We've all seen the Doctor react to cruelties, large and small, and fighting tyrannies is his stock in trade. But when have we seen him face unrequited love? I can think of one or more Companion that might have been in love with the Doctor, but when have we seen the Doctor love somebody who didn't love him back?
Please note, I'm not trying to incite a "Bestest and Mostest Beloved Companion EVAR" debate. I'm only interested in reciprocity, not relative strength of feelings.