Isaiah 9:1 (King James Bible) and afterward did more grievously afflict her by the way of the sea
As discussed under 1 Nephi 17:25, the earliest Book of Mormon text consistently has the nonstandard grievious (spelled in various ways) instead of the standard grievous. This dialectal form even shows up in the Isaiah quotations, here in 2 Nephi 19:1 and also in the following chapter:
In both of these passages, the King James Bible has, of course, the standard form grievous instead of the dialectal grievious. The critical text will restore the nonstandard grievious in all ten cases in the Book of Mormon text, including the two cases involving Isaiah quotations (2 Nephi 19:1 and 2 Nephi 20:1). For a complete discussion, see 1 Nephi 17:25. A similar situation occurs in the case of toward(s): Joseph Smith clearly favored towards, even when he dictated the Isaiah quotations (the standard King James Bible has only toward ). When supported by the earliest textual sources, towards will be maintained in the Book of Mormon Isaiah quotations. For discussion of toward(s), see 1 Nephi 21:23.
Summary: Accept the nonstandard grievious the two times that it occurs in the Isaiah quotations, here in 2 Nephi 19:1 and in 2 Nephi 20:1.