Yeah I know it would be hated and probably tank in sales. But there are at least a dozen of us that would like it.
What I mean is a game where if you kill some NPC, do some specific thing, throw away some specific item that you (at the time) consider useless etc you simply can not finish the game AND the game doesn't tell you what specific action it was that made the game unfinishable.
You just do what you do and at some point you reach a part of the game and it can at least be so kind to tell you that because of your previous actions you can't proceed further.
To develop this even further it might even give some weight to "moral" choices, imagen you get the choice to spare or kill a character if you spare that character (that so far in the story hasn't been portrayed as inherently "bad") this has a ripple effect that the character kills some other character that is necessary for progression. Or on the flip side you chose to kill a character that turns out to be key later in the game. It's just that the consequence isn't clear until 15 hours down in the progression.
Or even you kill (for shits and giggles) an non descriptive NPC, just that you didn't know that that particular NPC would give you a key quest further on. Or even make it more advanced you kill a NPC, but in the back ground the NPC has a story of being friend/spouse etc to some more importan NPC that then does not give you a key quest for killing the first NPC.
But the important part is that you will not be informed immediately that you made something wrong and when you reach a point in the game where it would matter you are not informed of what you did wrong.
Yeah I know, as I said earlier, that this wouldn't fly with 98% of gamers. But we are a handful of people that would like this. Of course you would be irritated when you realized you put 5, 10, 15 ,20 hours of playtime into something you can't finish.