What if God gives one the power to do so, and arms one with a flaming sword forged in the fires of righteousness?
Only if He also gives you winged sandals.
Then why not arm his angels with that to begin with?
Even angels have trouble with demons. Gabriel, in the book of Daniel, was held up 21 days by a demon called the Prince of Persia, until Michael the Archangel came to help.
I believe we have the power to cast demons out, but not to kill them. Though man has the power-through and from God- to cast out demons, I think confronting an actual demon needs to handled VERY, VERY soberly. Too many act flippantly about the power of angels and demons, AND "THEIR" authority over demons.
Too many think of themselves as more than equal to an angel, by the power of God. And yet, other than the Apostles after Pentecost, anyone who is described as seeing an angel fell on their face.
Can WE do as the Apostles? Yes. But that is a spiritual battleground that one better be VERY, VERY ready for.