Should I make up the prayers I performed behind an imam who cursed Allah the Almighty, knowing that he did so, and what is the expiation for this action?

Whoever reviles Allah Almighty, or His Book, or His angels, or His messengers, is a disbeliever and outside the fold of Islam. It is not permissible to pray behind him, by the consensus of the Ummah, whether he is an original disbeliever or an apostate. Whoever prays behind him while knowing his state must repeat the prayer. Al-Shafi'i stated that a disbeliever cannot be an imam, and prayer behind an apostate is not valid until he outwardly repents. Al-Shirazi emphasized that the imamate of a disbeliever is not valid because he is not qualified to lead the prayer. Ibn Qudamah added that prayer behind a disbeliever is not valid under any circumstances, and whoever prays behind him must repeat the prayer.

Ibn Uthaymeen mentioned that prayer behind a disbeliever is absolutely invalid, whether his disbelief is by belief, word, action, or omission, and that whoever mocks Allah, or His Messenger, or His religion, is a disbeliever. He pointed out the difference of opinion among scholars regarding one who prayed behind a disbeliever and did not know his state until after the prayer, whether he is obligated to repeat it, and he favored that the prayer of the ignorant person is valid.

Therefore, prayer behind an imam who reviles [Allah or His religion] is not valid, and the worshiper must repeat the prayers he performed behind him until he is reasonably certain that he has fulfilled his obligation.