As a reviewer, should I act when the second reviewer did not seem to review the manuscript carefully? I reviewed a manuscript and suggested a major revision, which was done in meantime. Now that I receive the revised manuscript again, I see that the 2nd reviewer wrote only one sentence in his review to the first draft of the manuscript, although there were major issues at the theoretical, methodological, and linguistic levels. Should I tell the editor that I consider such a review insufficient?
I see that the 2nd reviewer wrote only one sentence in his review to
the first draft of the manuscript, although there were major issues at
the theoretical, methodological, and linguistic levels.

Are these issues not addressed in the revised submission (based on your comments)? Have the authors addressed all your comments carefully and satisfactorily?

Should I tell the editor that I consider such a review insufficient?

I would not do this. It is the job of the editor to see whether the reviewer has done justice to the article.

However, if you think there are still some issues with the revised manuscript, give it a fresh read and add more comments, e.g.
&quot;I can see that the authors have addressed all of my previous comments. But, I still see that the article could be further improved if the following few points are addressed...&quot;