The man dumped in the swamp.
So the writers went out of their way to tell us that the patient being dumped in the swamp was still alive at the time. I doubt they would do this just to reveal he died in the swamp later that night. To me it appeared like heavy-handed foreshadowing that he is still alive and a candidate to be the Green Meanie, coming back to get his revenge on the hospital that left him for dead.
Everyone is suspecting Taylor, Kirstie and Stamos' characters on IMDB but I haven't seen anyone bring up this guy. I think there's a super strong possibility of him being involved in/behind the killer conspiracy this season unless it's a massive red herring. Only thing is that in the current timeline he would be a middle-aged black man and we have none of those on the show, so he can't be anyone we know.
Although, I was high when I watched this.