superstars get a lot of attention from bosses. but bad apples deserve even more. a growing body of research suggests that having just a few nasty, lazy or incompetent characters around can ruin the performance of a team or an entire organization—no matter how stellar the other employees. bad apples distract and drag down everyone, and their destructive behaviors, such as anger, laziness and incompetence, are remarkably contagious. leaders who let a few bad apples in the door—perhaps in exchange for political favors—or look the other way when employees are rude or incompetent are setting the stage for even their most skilled people to fail. it's crucial for leaders to screen out bad apples before they're hired—and if they do slip through the cracks, bosses must make every effort to reform or (if necessary) oust them.