We’re taught to find mentors who inspire us. But some of my most profound leadership lessons didn't come from a role model—they came from a nightmare. We are instructed to seek out the icons, the titans of industry, and the charismatic visionaries whose footsteps we can follow and rightly so. We should look for the "North Stars" of leadership. But there is another kind of teacher—one that is often more profound, more visceral, and more permanent in our memory. These are the l