Sometimes there is an employee who will not perform, cannot perform, or has a personal agenda inconsistent with the mission of the organization. In that case, the manager may have no other option but to take serious action, including termination. But that approach is a last resort. Part of any leader's job is to teach, coach, and improve the performance of employees. When efforts to improve job performance fail, there may be no other option but to get tough. I suggest the "three strikes and you're out" approach. This "get tough" approach shouldn't be required very often - perhaps for one or two employees out of a hundred. If it's required more often, something is wrong - probably the selection process wasn't thorough enough.

Firings
Personnel selection