This grammar does exist on another page, but I believe the old page did not include enough of the other possible meanings in English, and I did not want to heavily edit the old grammar page.
[kurai / くらい] with a negative predicate indicates a superlative. (Mr. Yamada is the most forgetful.)
It also expresses the idea of "at least." ?くらい in this use implies that the degree of a state is such that one cannot expect much more than X from that state.
Ｓのは?くらいのものだ expresses the idea that the speaker cannot think of anyone or anything else but ? that meets the description in Ｓ. In other words, ? meets the description in Ｓ to the highest degree among those the speaker can think of.
Ｖ1くらいならＶ2ほうがましだ expresses the idea the one would rather Ｖ2 than Ｖ1.
A related is expression is [hodo]. This can replace くらい *sometimes,* such as in examples #6081, #6082, and #6083.
does matter which one you use, or are くらい and ぐらい interchangable?
pupurun, it doesn't matter. Both mean the exact same thing. It just depends on your preference.
how is it different to hodo? is it that literally, kurai='this little' and hodo='this much'??
I think this grammar point is a little misleading, くらい､ぐらい means approximately, about, almost. it is used to state unspacific amounts of what comes before it. it does not carry a meaning of minimal amount, rather than, so〜that,the least or the only.
I think that you need to look at other sections of each of the examples to understand their true meaning.
#6085 does not translate to he is the only one. if you wanted to say he is the only or no one else could do the job, you would say. 今彼しかこの仕事ができません。or 今この仕事ができるのは 彼だけです。
because you use ぐらい your saying that if it wasn`t someone that has about as much (unidentified ablility) as he does they couldn`t do the job.
The next example #6086
the real operator in the sentence is the last part. ”ほうがました” and くらい is not nessasary to hold the meaning I would rather die than do such a thing. そんなことするなら already has the meaning.