He will dismiss when there is no job to be done. But always, he will search for a way out, a way to avoid the dismissal. It might mean demotion, or transfer to another department. The Boss knows that when the company hires people it makes a commitment to them. He will do his utmost to honor that commitment.
Dismissal is a failure of that commitment, on both sides.
Next time you are faced with a potential dismissal situation don't avoid the issue, but try to avoid the dismissal. Remind yourself that, whoever the person, he or she is a human being with a family and a face to maintain. So sit back, give the issue a little more time, think extremely carefully about it. But in the end you must decide. If the answer is dismissal, be scrupulous in handling it with dignity and compassion.