Can you give me any advice on how to handle doing something awful to someone else?

Two of my students blatantly plagiarized their last assignment.

I would have been fine with them working together (and even would have encouraged it). But they have some sentences that are word-for-word identical.

We have a zero-tolerance policy for cheating. I have no choice but to fail them for the course.

One of them is sneaky and dishonest and I had suspected that she cheated on a previous exam anyway. I will not be sorry to see her go.

The other one is very earnest and sweet but so completely lost and was clearly in over his head in this class.

Much as I dislike the one student, I feel horrible that I have to do this to them.

Have you ever had to do something similar? Any words of guidance?