I've only had one get ugly. Usually when I have to fire someone they know it's coming; and have known for a while. I'm very clear as the documentation of non-performance escalates. I'll often start by saying "your actions are what brought us to this point" to make sure they know THEY are the responsible party, not me.
Fired bunches of them but almost always with good documentation. We had a three strikes policy...three 'interviews' and you were gone. At the end of the second one my favorite line was " You have two strikes against you, and a fast ball coming..."
