The lion is come up - Nebuchadnezzar, king of Babylon. "The king (Nebuchadnezzar) is come up from his tower." - Targum.
The destroyer of the Gentiles - Of the nations: of all the people who resisted his authority. He destroyed them all.
Rather, A “lion” a “destroyer” of nations: a metaphor descriptive of the impending calamity. A lion is just rousing himself from his lair, but no common one. It is destroyer, not of men, but of nations.
Is on his way - literally, “has broken up his encampment.” Jeremiah uses a military term strictly referring to the striking of tents in preparation for the march.
Without an inhabitant - The final stage of destruction, actually reached in the utter depopulation of Judaea consequent upon Gedaliah‘s murder.