[Harvard Business] Poor leadership in good times can be hidden, but poor leadership in bad times is a recipe for disaster. To find out why leaders fail, we scrutinized results from two studies: In one, we collected 360-degree feedback data on more than 450 Fortune 500 executives and then teased out the common characteristics of the 31 who were fired over the next three years. In the second, we analyzed 360-degree feedback data from more than 11,000 leaders and identified the 10% who were considered least effective. We then compared the ineffective leaders with the fired leaders to come up with the 10 most common leadership shortcomings. Every bad leader had at least one, and most had several.