So, I've edited the question to hopefully give more clarity on the situation:
I've recently learned that my friend ( A ) assisted in plagiarism for another student ( B ) by completing the vast majority of a final-project in a class I also take with student B. I know B doesn't deserve the almost-perfect grade he will receive because of A's work. I feel terrible because I know how much effort I and others personally contributed to our own projects and it makes me feel like everyone else's work has just been invalidated.
I know, beyond any doubts, that this is what occurred:
B has struggled in this class. A is experienced with the class, the professor, and the subject matter. A has been helping B with other assignments, sometimes assisting more than he should, but otherwise not at any level I would deem "plagiarism."
B asked for help with the final project in this class. A, of course, obliged. After helping for a little bit, the due date was imminant and B's project was still in the beginning stages. At this point A realizes that he has basically been completing the project himself, but feels morally obligated to not "leave him stranded," so A fully completes B's project out of a personal, moral obligation to himself. Personally being friends with A, I know that this was a momentary lack of judgement, and I know he knows much better than to cheat.
A has done all of the work on the project and B is going to pass it off as his own work.
Looking at the College's plagiarism policy, the worst that will happen to the student B is:
Failure in the course in which plagiarism or dishonesty occurs.
For my friend ( A ) that knowingly plagiarized:
Loss of all credit for that semester and suspension for the remainder of that semester.
My friend A has struggled this whole semester, academically and financially, to attend the College and it would be horrific if he had to leave and all of his work be for naught. I find it also unfair that, for what A found as a moral crossroads (helping his friend), and a momentary lack in judgement, will cost him so much more than the punishment B will receive.
I want to report it, but if I do (even anonymously), B will only tell the administration that my friend helped him. I can't be responsible for that.
What can I do in this situation? Report it? Keep it to myself and hope the professor knows? Meet with the professor and have an honest discussion about how I feel and how I know my friend knows the ethics of cheating but became morally confused in this instance?
I guess the overarching question here would be: what outcome provides the best result for A while simultaneously reporting B for plagiarism?