I have my doubts that this is going to be about Graham. The way the synopsis is written, it would seem that everyone believes Regina to be the culprit and Emma is defending her. Let’s not forget about Emma’s “power” and since Regina did kill Graham she would know right away she is lying.
in my opinion, the possible characters would be : Archie / Red / Blue / Leroy / Granny.
I really don’t wish death upon any of these characters but it would be gripping to see any of them die.