I want to add that dealing with difficult employees is a slippery slope and fraught with many pitfalls.It's the reason why employers must have sound policies and keep careful records (performance records, statements, impartial witnesses, dates, times, places, circumstances etc.).
Employment decisions must be amply justified so they can be upheld. Problem employees should be offered (well documented) counseling, occupational safety training, job reassignment etc. Employer can then demonstrate that all steps were taken to help a problem employee succeed. If following that, there's still no improvement, decision to terminate may follow. Employer is bound to demonstrate good faith and 'due diligence' so decision to terminate can be protected.
Why go to all that trouble? Because subjective observations such as 'not well liked', 'irresponsible', 'unfriendly' or 'not a team player' won't hold up in court. Similarly a label (i.e. narcissist), won't do either unless in this case, a valid diagnosis from an accredited mental health professional can be procured. Even then, company would have to demonstrate how someone's narcissist behavior affected a particular workplace, adversely enough to merit termination (discrimination, demotion etc.).
When a disgruntled ex employee decides to sue and wins it's because Company policies are lacking or someone didn't exercise due diligence in their record keeping. Class action lawsuits over wrongful terminations have cost employers millions in liability awards.