"Then We will surely extract from every sect"—meaning from every nation—"those who were most defiant against the Most Merciful."
Muhammad said: "Ayyuhum (which of them)" is in the nominative case, which is the majority reading. It signifies: "Those who are said to be: which of them is most defiant." It has been said—and God knows best—that the meaning is: He shall begin the punishment with those who are most defiant, then those who follow them.