It really is important and it's amazing what happens when you get to think more about the antagonist. I look forward to this assignment every time I prep. I think the author needs to love their antagonist just as much as they love their protagonist, but so many of us get too caught up in our hero. Having to create a story where the antagonist is the sympathetic character helps us fall a little in love with them.

And, of course, we all know what happens when we authors fall in love with our characters. We break them.

The difference most of the time is, nobody puts the antagonist back together again.