Being a leader means making difficult decisions sometimes. What do you believe is the hardest decision a leader can make?

This is a good question.

Firstly, let us be clear.  Letting somebody go is rarely a difficult decision to make. (The only exception is when firing somebody might lead to the company going bust.)  On the contrary, it is often quite easy.  However, implementing that decision can be achingly difficult. 

An example of a genuinely difficult decision is when there are five or six courses of action open to you.  There is plenty of information available, and adequate time.  A number of intelligent and informed advisors are helping you, and being helpful, but the decision is unequivocally yours.  Of the courses open to you, all except one are certain to lead to the death of your organisation. None of your advisors have a firm view because nobody can foretell the future.  It's your task to decide which path is the right one. 

If the context is military it's even more serious - if you get it wrong, the mission fails and everybody dies.

Definitely, most difficult decision is to terminate somebody's contract, when the only reason behind staff reduction is cost cutting

I Believe the hardest decision would be letting go off anyone from the team or in the Company.

Thank you. I agree with experts answer.

In depth360 degree review, thorough analysis, prior taking tough decision.

Be responsible, don't regret and stand by what ever decision you have taken (whether right or wrong).

In general

The most difficult decisionsIs a decision that would apply to the largest possible number of people Hard to please everyone

Thanks for invitation,

I do believe that the hardest decision is to "excluding" a work team member due to disqualifications. 

it is to terminate an employee who is not showing a  high performance in his job . This decision must be based on engrained in logic, to continued company success, and maintaining a positive work environment. and It is based on actual and annual work evaluations to ensure that it is done professionally and based on a factual assessment of the employee’s performance. 

IN AN UNCERTAINTY SITUATIONS WERE ISSUES ARE UNCLEAR,UNPREDICTABLE.THE LEADER IS FORCED TO BRAINSTORM VERY WELL BEFORE ARRIVING AT CONCLUSION.UNPROFESSIONAL ISSUES CAN MAKE THE LEADER TO WIDELY GAIN KNOWLEDGE ON THE PROCEDURES OF  GETTING POSSIBLE OUTCOME THAT MAY LEAD POSITIVE DECISION MAKING.

Thanks

I support the answer given by colleague Mircea.