Those are the polytheists from the Quraish of the Arabian Peninsula, and the Jews whom Allah (swt) has cursed. Allah’s curse means expulsion from His mercy and falling in disgrace and destruction.

(… أُولَٰئِكَ الَّذِينَ لَعَنَهُمُ اللَّهُ ) (Those are the ones whom Allah has cursed;…): Allah (swt) cursed and expelled them from His mercy because of their disobedience, their aggression against people, their lying to the Torah and their distortion of it, and igniting the fires of wars that Allah (swt), due to their hatred for the message of our Prophet (saws) and against all the Arabs.

( وَمَن يَلْعَنِ اللَّهُ فَلَن تَجِدَ لَهُ نَصِيرًا… ) (…and he whom Allah curses – never will you find for him a helper.): Because if Allah (swt) expels someone from his mercy and seizes him for his sin, no human power can stand in the face of Allah’s power and he will not have any helper.