The first time I did the Langdale 'Bad Step' it was possible to squeeze underneath the chockstones and emerge at the top. This would have been early 1970s. It's since become blocked by debris. The REALLY bad step is probably the Witches Step, on Arran. It's polite name is the Old Ladies Slot or Step. I think the literal translation from the Gaelic may be ruder than that - Ceum na Cailleach.