Unbelievably stupid ending

I generally agree with your points Andrew but I'd like to add one more that makes their action even less plausible. During their relatively unmolested drive we never see any efforts to seek gas or refuge. They saw the gas gauge. They knew just mindlessly driving the car out of gas was foolish and yet that's exactly what they did. Were we supposed to assume they had made some efforts? Was the movie running too long to show this, to show us HOW it was that the fight and hope they had carried with them from the store was now extinguished? No, it was definitely not time constraints. Darabont could NOT show us this because for this ending twist to have the message and impact he wants they have to do this in an obviously preemptive way, they have to UNEXPECTEDLY crack. He has to contrive and manipulate so clumsily. But this kind of cracking - no effort, no struggle, and then killing your own kid! before hope was well and truly lost, and before there was even an imminent threat! was so far out of character for our group of plucky fighters it was as if they had been replaced by defeatist impostors. (if you had a group of annoying defeatists all along then the end would have worked). We identify with the people in the car and when they do this we FEEL violated. All so the director can work in the shocking content of a dad blowing his own kid's head off and then see him punished by the 'twist'. This is a fool's gold ending. It's a low blow cheat! Low hanging rotten fruit any real writer would reject out of hand. It only works if you ignore the characters and their context. It only works if you rationalize all that away and start claiming that 'yes, it felt rushed' but 'we cannot imagine how they felt".

"Murder their own kid while the kid is looking at him in fear without telling the kid the reason or permission because of uncertainty... that's something someone mentally ill would do."

A mentally ill person, or someone who's scared $hitless.

"The idea that 4 sane adults all just happen to have the same mind too and be bobble heads to mass suicide + murder of a child is farfetched."

People are capable of anything in the face of disaster.

"Exactly, Drayton and co. had no way of knowing if there were creatures (good or bad) or humans (good or bad) outside or just nothing there. Every day people have a lack of knowledge that's potentially deadly (bad drivers on the road, unpredictable lethal weather, criminals, hiking trips go terribly wrong, brain-eating amoebas, flesh-eating bacteria, terrorists, etc) and there aren't mass suicides over that lack of knowledge (unless they have a mental illness, like Munchausen syndrome). For a once-sane person to commit suicide because of a lack of information is improbable, but for 4 once-sane adults to all at the same time coincidentally agree to mass suicide + child murder because of it is unrealistic."

Except this was a disaster that no one foresaw and were completely unprepared for. For a once-sane person to commit suicide because of lack of information is improbable, that is true, but they may do so if things look incredibly bleak. Things have happened at the Louisiana Superdome during Hurricane Katrina, including three-four suicides, murders, vandals, etc.

"I generally agree with your points Andrew but I'd like to add one more that makes their action even less plausible. During their relatively unmolested drive we never see any efforts to seek gas or refuge. They saw the gas gauge. They knew just mindlessly driving the car out of gas was foolish and yet that's exactly what they did. Were we supposed to assume they had made some efforts? Was the movie running too long to show this, to show us HOW it was that the fight and hope they had carried with them from the store was now extinguished? No, it was definitely not time constraints. Darabont could NOT show us this because for this ending twist to have the message and impact he wants they have to do this in an obviously preemptive way, they have to UNEXPECTEDLY crack. He has to contrive and manipulate so clumsily. But this kind of cracking - no effort, no struggle, and then killing your own kid! before hope was well and truly lost, and before there was even an imminent threat! was so far out of character for our group of plucky fighters it was as if they had been replaced by defeatist impostors. (if you had a group of annoying defeatists all along then the end would have worked). We identify with the people in the car and when they do this we FEEL violated. All so the director can work in the shocking content of a dad blowing his own kid's head off and then see him punished by the 'twist'. This is a fool's gold ending. It's a low blow cheat! Low hanging rotten fruit any real writer would reject out of hand. It only works if you ignore the characters and their context. It only works if you rationalize all that away and start claiming that 'yes, it felt rushed' but 'we cannot imagine how they felt"."

You have some interesting points, but at the same time, with regards to your complaints about characters "being so far out of character", I heavily disagree with them - in relation to the story, which is all about communities and people compromising themselves in the face of disaster, allowing fear to cloud their judgements and thereby causing them to make some of the dumbest, heinous decisions and actions imaginable, the ending reinforced that theme even more. Drayton at a glance is a rational person, but at the same time, he and his fellow travellers were also hypocrites; they were the very things they criticised the people in the store of being. They may have gotten away from the store and the threat represented by the people within them, but that doesn't mean that Drayton and co were immune to fear, nor were they immune to bad decision-making - they're human. To have Drayton do what he did, it takes away any heroic certainty. Now, could they have drawn it out more, with scenes showing survival and a gradual descent of spirit? Perhaps, but there's the issue of pacing and the threat of having a story running on for too long, even the threat of making the ending predictable. As a movie, the ending works as a fine bookend to what the story is about. Could those aspects be fitted into a TV series? Possible.