Still, he could have told him to F#ck off. He didn't have to kill the poor bastard.
You commit numerous federal crimes with a guy, kill people, etc. and want to leave him alive when he has been harboring resentment for you for awhile now and probably always will?
It was only a matter of time one way or another where Christopher would cause a clusterfuck in Tony's life.
Long as I remember The rain been coming down. Clouds of Mystery pouring Confusion on the ground. Good men through the ages, Trying to find the sun; And I wonder, Still I wonder, Who'll stop the rain.