(You have to hack in at a hardline!)
"It appears," says Ariadne, "that you can't actually kill Melitus. The others tried. Physical damage means nothing to him. They hacked his head off; it didn't seem to bother him much. I am working on the ideas that what you see is not actually HIM; all he said about it was that this is the Matrix and everything is just an affectation.
"You simply cannot harm him."