We’ve all worked with people who are star performers but have one serious personality shortcoming that makes life difficult for everyone, limits their effectiveness, and often proves to be their professional undoing. One person, for instance, constantly takes on too much work. Another scorns the behind-the-scenes politicking needed to win support for most projects. A third sees the downside in every proposed change. In the words of one executive we worked with, such people are “95% brilliant, 5% disaster.”