The finish shot is no fun, but humaine and it should be as quick and as painless as possible.
Side note:
On our last hunting trip, my buddy, who is new to deer hunting, happened to be the first one to the deer that had been shot in the vitals, but not expird yet. He went to finish it off, but didn't really think about what he was doing. He shot it in the neck as the thing was facing him!
The bullet went in the neck, down the spine (between the spine and the strip loin, believe it or not), never touched any of the guts! Hit the pelvic bone, shattering it of course and bounced between the two hind quarters several time(making quite the mess I might add)! I found the bullet between the muscles and the skin on the hind leg.
It was a messy situation to field dress. I had no idea what I should be cutting! And it ruined quite a bit of meat on those quarters!
I definetly learned a lesson from it! Never shoot when they are facing you, even for the finish shot! I just hope he learned a lesson, probably not seeing, I was the one cleaning up the mess!