The Other Side
The best managers, like the best lawyers, know how to argue the other side of the case.
They don't leap into rigid advocacy. They carefully test the ropes that bind together the arguments. They are reluctant to accept as gospel someone's assertion that "something" happened.
They may inwardly smile when hearing that there is only one explanation for conduct. Having been around, they well know the multitude of motives that can cause people to act against self-interest and logic.
Their ability to understand the other side is one of the most valuable commodities in the workplace.