In Romans 12:19 Paul writes, Beloved, never avenge yourselves, but leave it to the wrath of God, for it is written, 'Vengeance is mine, I will repay, says the Lord.'
The assurance of Scripture is that the Lord will repay all the cruelty and injustice done in his world. This ultimate judgment is seen by John in his vision in Revelation 18:4–8 where Babylon represents all the oppression and cruelty done by the powers of the world.
What happens in Nineveh is simply a foretaste of the Lord of hosts calling cruelty and oppression in his world to account.
13 Behold, I am against you, declares the LORD of hosts, and I will burn your chariots in smoke, and the sword shall devour your young lions. I will cut off your prey from the earth, and the voice of your messengers shall no longer be heard.