What is the meaning of "Mi Yakum Li Im Mere'im"?
Sotah 13b: When Moshe died, Hashem was saying this. Rashi (there) - who will rebuke them for My sake?
Rashi: Whose merit will stand for us among these evildoers?
Radak (16-17): This is a sign and witness that Hashem sees our affliction. If not for this, already we would have been eradicated. The nations want to eradicate us, just Elokim does not let them, like He promised us "v'Af Gam Zos bi'Hyosam b'Eretz Oyveihem Lo Me'astim v'Lo Ge'altim Lechalosam" (Vayikra 26:44). So the author says on behalf of Bnei ha'Galus - who stood for me among these evildoers? "Im" is like against; the same applies to "u'Melech Alkum Imo" (Mishlei 30:31; he fought with him). It is as if Hashem fought them to annul their counsel.
Malbim: I almost despaired from salvation - who would stand for me among these evildoers, if not that Hashem helps me (verse 17)? Based on nature, I cannot be saved.