A worthy topic of discussion, considering the number of modders on HLP with design aspirations. I thought it might be fun for us to dig up various examples, particularly because I found an obnoxiously glaring one last night.
My example? Dishonored: Knife of Dunwall DLC Mission 1
For those unfamiliar, Dishonored is predominantly a stealth game with combat elements and a wide latitude in playstyle - it allows you to proceed by killing everything and everyone in your path, by avoiding everyone and being a complete ghost, by non-lethal neutralization, and various combinations thereof. The game has design elements that make all of these playstyles equally viable, and an achievement system that reflects that. It is a very well-crafted game and has clearly been painstakingly balanced... which is perhaps why this example is so baffling and infuriating.
In the first mission of the Knife of Dunwall DLC, you infiltrate a slaughterhouse (of whales) and interrogate its owner, who is really not a nice person. You can then lethally or non-lethally dispose of him, and finish out the level.
In the course of my game last night, I painstakingly cleared the level by knocking out enemies and stashing their slumbering bodies in secluded areas, being spotted by no one in the process. I've been doing my utmost to obtain three achievements in the playthrough: complete non-lethal, complete non-detection, and finish the game with a certain amount of coinage left to me. This means I am scrounging the whole level for every scrap of loot I can find.
I knocked out my primary objective, and then stashed him in a shipping crate to get rid of him non-lethally. I then backtracked through the level, knocked out the final remaining enemies, and collected the loot. Finally, I went to depart a certain area, then heard a sudden commotion. I turned around, and the game had spawned an enemy corpse in plain sight, with three live enemies around it, who immediately alerted and began searching. I reloaded, tried exiting a different way. Same effect. I tried several times, and determined that every time I knocked out the last enemy in one part of the level, it would spawn the corpse and three live enemies around it. I eventually bypassed this by leaving one enemy awake in that part of the level, and heading toward the exit... only to find the same thing happened in a different part of the level I had already cleared, with no way to avoid it.
To summarize: in a stealth game in which one playstyle is rewarded by knocking out all enemies and hiding them to proceed non-lethal with no detection, the game actively spawns enemies if you attempt this into a situation where you cannot prevent detection. Furthermore, when played through to the end of the level, the game counted the corpse it spawned as a player kill. Let me repeat that: in a non-lethal run, the game spawned an already-dead NPC and counted that as a player kill. There is no warning or explanation whatsoever that this would happen.
The end result is that I am replaying from a much earlier save, and I will refrain from knocking out all enemies in a single area after locking up my target, because that seems to spawn a railroaded game change that ruins player approach with no ability to prevent it.
This is bad design. Anyone else have some glaring examples they'd like to share? Keep in mind this is about bad design in otherwise good games, not simply bad games.