Due to his efforts on behalf of missouri, henry clay became known as the “great debater.” the “leader of congress.” the “great compromiser.” the “slavery supporter.”

The correct answer is: "the Great Compromiser.”

Henry Clay (1777-1852) was known as The Great Compromiser due to his crucial participation in the issuing of the Missouri Compromise in 1820, that ended a sectional crisis over slavery.

The Missouri Compromise established the incorporation of the state of Missouri to the United States as a slave state, and the simulatenous admission of Maine as a free state, which would keep the balance of power between slave and free states, in other words, between Southern and Northern states in the US.