Pseudoephedrine
Should be playing D&D instead
My go-to example of very bad DMing isn't quite this extreme, but also similarly negates player agency. Long story short, some NPC soldiers have been captured by the local villagers. Another PC and I decide to steal the highest-ranking prisoner so we can sacrifice him to our god and ruin a peace the villagers are trying to make with the local lord. When we do a quick inspection of him, the NPC is described as having a bandaged ear but otherwise able to walk, talk, etc. As we're hauling him out into the woods, he suddenly drops dead - he was bleeding out of his ear the entire time sufficiently badly that blood loss has suddenly caused him to keel over. We therefore can't use him as a bloody spectacular sacrifice to break the coming peace.Dude, you really don't know the kind of DMs I am talking about.
DM: Your 15th level character comes to a field, what do you do?
PC: I start walking across it.
DM: a 10' pit opens up in front of you and you fall in. You break every bone in your body, what do you do?
PC: From a 10' fall? For a 15th level character? I guess I try to climb out of the pit.
DM: You can't move, all of your bones are broken, what do you do?
PC: I look around to see what there is in the pit that might help.
DM: You can't see anything, you are face down. Your neck is broken and you can't move your head.
PC: I cast levitate.
DM: You can't cast spells, you are in too much pain.
PC: I call for help.
DM: You are too weak to do anything more than moan, what do you do?
PC: I pray to my god to help?
DM: You can't, it hurts to much to even think.
PC: [salty] Well I guess I lie there and bleed to death, then.
DM: Well don't take that attitude!
This led to a lot of debate, and created the term "bleeding out the ear bullshit" and "bleeding out the ear" as a shorthand for whenever a DM was seen as using arbitrary and unfounded claims about the world to undermine the players.