Great boss provides leadership, direction, critique, and a positive example which allows each employee to fulfill their potential while serving the organization. A bad boss would be one who fails in at least one of these areas, but to be immoralized as one of the worst bosses, you've got to create an environment so toxic that none of these elements are present or they are overshadowed by the deficiencies to such an extent that employees are unable to approach their potential or even function.