The thing about the execution in Braveheart is all tha stuff that Gibson couldn't show, and which is presumably happening out of camera range during all those agonized close-ups. If you want all the grisly details look up an article on "hanging, drawing and quartering". Just don't do it after a heavy meal. So I'd say that one pretty much trumps anything else in film and will continue to do so unless someone puts one of Saddam's "lower the guy into the plastic shredder an-inch-at-a-time, feet first" exectutions in a movie.
The scene in Meet Joe Black.... the one that involves the bus and Brad pitt. That one was not only painful to watch, but it sure as hell caught me by suprise.
I forgot about that. Don't know if he died.. but that scene is made me sick to watch.. bah! (loved the movie on the whole, though, and the scene got across the point in regards to depravity)
In Friday the 13th part 6 where the cop who attacks Jason gets bent over and folded in half.
When the guy who is the head of public transportation(I think that's what his job was) tries to rescues the guy in the subway train, and has to jump in the lava to do it in Volcano.
When Murphy gets shot literally to bits by the men he's trying to apprehend, anmd lives through pretty much all of it in Robocop.(Not sure if this counts)
Also in Robocop when on of the bad guys gets soaked in the toxic sludge and starts to melt, and then is hit by the car while walking down the road.
Mary Elizabeth Mastrantonio in The Abyss. Painful to watch, painful to happen, painful for my throat as I scream "Get swimming, Ed Harris! Don't just wait for her to die! Get a head-start!"
Although it's definately a better scene the way it is!