Speculater, rok temu

The original Neverwinter Nights, you could kill main story NPCs and lock yourself from progressing. If you saved after this without realizing your mistake because you’re dumb, you have to restart.

Also, the original pre-order Ocarina of Time, if you did the keys on the water temple in the wrong order, it made the temple nearly impossible. Data sleuths have found a way to progress, but 14 year old me spent 20 hours trying to figure it out and quit the game.