The 1837 edition removed the relative pronoun that from this verse. We cannot be sure whether this deletion is intentional or not. Joseph Smith did not mark it in the printer’s manuscript. When we compare similar texts containing “all (that)” followed by a pronoun, we find that the relative pronoun that occurs in most cases (12 out of 16 occurrences). The ones without the that are marked with an asterisk in the following list:
One interesting contrast occurs in Alma 24:11; there we have examples of both types (one with the that and one without). This variability shows that in each case we should rely on the earliest textual sources to determine whether that follows all. There does not seem to be much tendency to edit out the that, so the 1837 change in 2 Nephi 25:23 could well be a typographical error. Note, by the way, that the 1906 LDS large-print edition restored the that (but probably accidentally since there is no evidence elsewhere to show that the 1830 edition was used to correct the text for that edition).
In addition to this general case, there are also six instances where the word all is preceded by a measure phrase. Unlike the general case, here we find that no that ever follows all in the Book of Mormon text:
It should also be noted that each of these refers to a portion of one’s possessions. For further discussion regarding the omission of the relative pronoun that, see under which in volume 3.
Summary: In accord with the earliest textual sources, restore the relative pronoun that in 2 Nephi 25:23 (“after all that we can do”).