Which two judgments did Amos see in visions and plead against, so that the LORD relented?

Answer: Locusts and fire

Amos saw swarms of locusts (KJV: grasshoppers), then judgment by fire; each time he pleaded, "How will Jacob survive?" and the LORD relented.

“This is what the Lord GOD showed me: He was preparing swarms of locusts just after the king’s harvest, as the late spring crop was coming up.”— Amos 7:1 (BSB)