Character you like that everyone else hates. Martha Jones. I really don't understand why people hate her so much. I mean yes, she came after Rose and she was in love with the Doctor. But think about it: how many of his companions had the strength to voluntarily leave him to save themselves heartbreak? Done thinking? Yeah, pretty much just Martha.
He almost kept them. When I was watching "Angels take Manhattan" I thought of this... Some of the hardest goodbyes for the Doctor. He had them both for so long. Donna and others were just as hard, but they were different at the same time. Rose and Amy... they were the first face that that face ever saw.