A couple of you have brought up that giving the villian emotions would make him less of a villian and more of a hero. Do you think this is a bad thing? Does a villian have to be super evil with no feelings except hate and anger?
Thing is, often times when the reader sees that there's a redeeming quality to a villain or if he's become jaded or they feel a bit bad for them, automatically the reader starts hoping that the villain seeks redemption. It's human nature to want to forgive. So I suppose that's kind of why it lessens the villain's villain-ness. And if the reader doesn't obtain this at the end, they may or may not feel cheated.
It is not a bad thing. I repeat, not a bad thing. Darth Vader blew up his daughter's planet containing billions of people. He murdered children! Then, when he sees his son in pain, he saves him. Voila, emotionally satisfying redemption.
And if they don't achieve redemption, then that only leaves the reader to pity them. Look at Voldy. The reader (along with Harry) felt bad for him, not because he grew up without love, but that he didn't know what love was at all.
P.S. The road to hell is paved with good intentions. Often those who do wrong do so thinking it is the right thing to do.