How to review a revised paper I have already rejected?
When you recommended rejection, you presumably listed a series of issues that made it unacceptable.  On the revision, you go back and repeat the list of issues and simply say for each one, "The revision has/has not corrected this problem".  If you reach the end of your list and all the issues have been corrected and no new issues have been introduced in the revision, then you say the paper is now suitable for publication. If the issues have not all been corrected, then you say "The paper is still not suitable for publication because the issues I noted previously have not been corrected."