Revelation 6:10

And now in loud voices they cried out, saying, "How long, O Sovereign Lord, the holy One and the true, dost Thou delay judgment and the taking of vengeance upon the inhabitants of the earth for our blood?"

Revelation 18:20-24

Rejoice over her, O Heaven, and you saints and Apostles and Prophets; for God has taken vengeance upon her because of you."

Treasury of Scripture Knowledge

Summary

Because thou hast spoiled many nations, all the remnant of the people shall spoil thee; because of men's blood, and for the violence of the land, of the city, and of all that dwell therein.

Bible References

The violence

Revelation 6:10
And now in loud voices they cried out, saying, "How long, O Sovereign Lord, the holy One and the true, dost Thou delay judgment and the taking of vengeance upon the inhabitants of the earth for our blood?"
Revelation 18:20
Rejoice over her, O Heaven, and you saints and Apostles and Prophets; for God has taken vengeance upon her because of you."