Why does it say "Zechor Hashem Cherpas Avadecha"?
Radak: The enemies revile us, and say that we have no salvation.
Malbim: You should recall their insults to us, for they insult us in Galus because we serve You!
What is the meaning of "Se'esi v'Cheiki Kol Rabim Amim"?
Rashi: In Galus, I bear their suffering and burden.
Radak: I bear my disgrace in my lap - many nations disgrace me. Everyone in Galus says so 1 . "Rabim Amim" is like Amim Rabim. Also "Avtit" (Chabakuk 2:6) is like Tit Av; "Mekom Sham Kever" (Yechezkel 39:11) means Mekom Kever Sham.
Malbim: I bear the insult, even though really, they insult You (verse 52)!
This is why it is in the singular. (PF)