Almost all leaders have “dark-side characteristics” that are placing organisations at risk, according to a new report.A 10-year study into the behaviour of UK managers found that 85 per cent have personality traits that can quickly turn from being desirable to destructive in times of stress. Swinging from being enthusiastic to being volatile or from shrewd to mistrustful, for example, “could spell disaster” for organisations and individuals’ careers, warns the study of 18,000 leaders.