Regarding 2 Thessalonians 1:6-9 and Revelation 19:11-21... Who can find THE BIBLE'S answer?

This is referring to the Battle of Armageddon. All the armies of earth will be gathered in Israel. Jesus will return to earth with His church at the end of the tribulation period. The armies will attempt to do battle with Jesus. It is those armies that are killed, not the general population.