After committing a series of brutal rapes, a young man must conceal his crimes when he supernaturally begins to feel the physical pains of one of his surviving victims…. His pregnant best friend.

First, don't give away the twist... his best friend.
Second, one assumes he's been concealing the crimes all along.
Third, supernaturally feels odd as the descriptor.

Suggestion:
A serial rapist begins to personally experience the physical trauma of his victims.

Well, it's your character and story. And you are fully conscious of the dramatic hazard zone you're working in. So:

A serial rapist struggles to conceal his guilt and crimes after he begins to feel the very pain he inflicted on a surviving victim?. his comatose, pregnant best friend.

The audience (hopefully) wouldn't watch to see an unrepentant rapist suceed, they wouldn't watch to sympathize with him or root for him. The exact opposite. You would want to see justice prevail, to see him get EXACTLY what he has coming! This is a script for a short film that never got completed in high school and I'm currently reworking now for the third time. Everyone who has read it in the last couple years tells me that they HATED his character (keep in mind one of his victims is his 5 year old sibling) and they couldn't wait to see him get what he had coming even when it seems he is in the clear. And thats what i want. I want them to leave the theater feeling...satisfied that justice will always be served in one way or another and if it isn't, you'll always reap what you sew. This character is vile in every way. Everyone in the world would be against him, they'll want to see him go down and go down in the worst way possible. And that is indeed what happens.