How to work with someone who’s negative, unimaginative, and defensive?

Is there anything more frustrating than trying to accomplish a big goal with someone who’s negative, unimaginative, and defensive? Thankfully, it’s been a while since I’ve tried. But I’ve had my share in the past, and I can tell you that nothing will kill an organization’s productivity and vision like a can’t-do person. But if this kind of cynicism brings a team down, what can lift it up?