I've had to fire people. The worst ones are the ones when you look at all the signs you should have seen that they would fall short of what you needed from them, but for whatever reason you chose to only see the hopeful signs and you hired them.
There's one in particular that haunts me. I won't give the person's name because that would achieve nothing positive, but when I think back to everything from the interview to the orientation period, I realize the red flags weren't just flying. They were soaring. I wanted it to work so badly that I failed to exeercise my best judgment and I paid a price for it. That was entirely on me.