Yes, I will tell you what this skill is; however, do you think that you can guess it before I do? I’m sure that you can come up with the standard list of leadership skills that every product manager has (or at least should have): able to deal with pressure, able to lead people, vision, positive attitude, creativity, etc.
However, those would all be good to have, but none of them would be the #1 skill that a product manager needs to have. Give up? The answer is …