I've encountered the expression the only one difference (as in, "The only one difference between these two cars is the color"), and to my ears it sounds wrong, excessively redundant, but the writer claims it is just for added emphasis.
Are there any good examples of usage for this expression? Google only gives me results of dubious quality.
If you want to list multiple adjectives at the same "adjective level" for emphasis, you have to make it clear that they are at the same level, or it sounds like you are violating the rules of adjective order: "The only one difference" sounds just as bad to me as "the green round small lump" or "a big large sizeable dog".
Ordinarily you can repeat the article to make it clear that you're effectively starting the description over:
- The one, the only, the single, the lone, the solitary difference....
- It was a big, a large, a sizeable dog....
Otherwise if two different adjectives do actually apply at the same level, you join them with and:
- The red and green shirt
- The ragged and torn coat
In the specific case of uniqueness, it is actually common to say "The one and only" as a form of emphasis.
It sounds unnatural and redundant, but at least the meaning remains clear: the only difference.
If I wanted to add emphasis. I'd rather use italics than redundant language.
Aside: Personally, I feel that if a writer tries to add too much "for emphasis", then it actually betrays a lack of confidence in the statement itself. If you feel the need to add multiple exclamation points after a sentence (??) (!!!), then it's probably a signal that the original sentence isn't emphatic enough.
