Amos prophesied two years before what event?

Answer: The earthquake

Amos's words came two years before the earthquake, when Uzziah was king of Judah and Jeroboam son of Jehoash king of Israel.

“These are the words of Amos, who was among the sheepherders of Tekoa—what he saw concerning Israel two years before the earthquake, in the days when Uzziah was king of Judah and Jeroboam son of Jehoash was king of Israel.”— Amos 1:1 (BSB)