Difference between “let alone”, “never mind”, “much less”, “still less”, and “not to mention”

Which of these five expressions can be used in front of the word “crossing” in the following sentence?

I was wondering if American and British English speakers would choose different ones. Many thanks.
Man: I proved that, when it comes to helping her, I would not balk at sticking my head into the lion’s maw, let alone crossing such common scum as Abelard.

You could probably use all five of them, although “not to mention” seems to not fit as well as the other four.

Ouch. As a sentence it’s a bit lumpy, whichever you choose. Is the “speaker” supposed to be despising Abelard, or consider crossing him a more daunting prospect than sticking his head into the lion’s mouth? The two don’t quite go together.

However, if the intention is to say that crossing Abelard was, by comparison, trivial, then “much less” is the one I’d go for. “Let alone” and “never mind” would suggest to me that crossing Abelard is the more daunting; “not to mention” would suggest it’s an afterthought; “still less” suggests that they’re both trivial, but crossing Abelard the lesser.

But I’d break the idea up into two parts: colon after “maw”, and then “crossing such common scum as Abelard was nothing” (or some such).

As the speaker sees it, crossing Abelard is even more dangerous than the unthinkable act of sticking his head into the lion’s mouth. Thank you.

Then “common” is the word that’s causing the awkward impression. It demeans Abelard rather than making him seem dangerous.

Then it wouldn’t make sense to use any of the constructions in which crossing Abelard is “less” balked at.

Incidentally, the story this line of dialogue comes from is set in the 13th century! So I was wondering if perhaps this “common” is meant as the derogatory term for people from low social class. I seem to recall hearing somewhere that BrE speakers used to use the word “common” in this particular sense. Is this no longer the case?

Yes, it is, and in a modern novel set in historical times, I wouldn’t see any harm in using it in that sense, even if a thirteenth century person might have said something else. The problem is that whether or not a person is “common” in that sense tells you nothing about how dangerous they are: whereas the sentence is (supposedly) trying to stress how much danger the speaker is willing to risk.

As an English English speaker, and keeping the sentence structure unchanged, I find that “much less” fits the intended sense best.

I think “nor even” is more suitable than anything mentioned, again, if the intention is to depict Abelard as more dangerous–that not-balking at him is a stronger claim.

I would stick with “let alone.” It is the phrase I most commonly use for that construction.

Only “not to mention” seems absolutely wrong to me. It’s difficult to explain why. I think it has to do with the focus. “Not to mention” is usually followed by something that emphasizes the point, while the OP’s construction is preceded by the emphasis. The point of the sentence is “Crossing Abelard is no big deal compared to what I am willing to do.”

“Never mind” does somewhat fit, but I would not really use it. I think it carries the connotation that what follows is trivial to the point of dismissal. The most common use of the term is to say “don’t worry about that.” As in: "What did you say? Never mind.

“Still less” just seems formal or archaic to me. “Much less” would fit in theory, but it still doesn’t sound right to me.

“Let alone” is always what I use in those constructions.

No, it was meant to be the opposite.

Then all four of the statements are incorrect. They all say that the first option is worse. And, frankly, so does the entire tone of the sentence. The guy is just “common” scum–not very scary. And putting your head in a lions mouth is something you are willing to do–so why use it as a comparison?

There really is no way to express the idea that it’s worse unless you say “Crossing Abelard is worse than putting your head in a lions mouth!” And then you are clearly saying that you would not cross Abelard, when the sentence is something you saying you are willing to do.

I take her claim as just having to do with her own problems with English. She got the two sides mixed up. Otherwise, the entire sentence doesn’t make sense.