it's usually accomplished by way of a flaming sword. But angels have other ways of torching their targets. There's the "Breath of Death" which is more of a caustic chemical burn. But the result is usually the same...a charcoal briquette that was once a human being.
The angel that commanded Joseph Smith, Jr. to have sex with various women chose to turn off the flame before showing the sword. There was some concern that Joe's priesthood could get burnt by accident...and that would have frustrated God's purpose which was for Joe to share his priesthood with as many women as possible.
There was reportedly an angel using a flaming sword at the entrance to the Garden of Eden. According to the story, after Adam and Eve were kicked out of the Garden of Eden Spa and Resort, they tried to sneak back in, but found their way blocked by an angel wielding a flaming sword. But experts and academicians generally agree that it was more likely flaming sticks being twirled by "fire dancers" in a Tiki show that was being put on for a special luau inside the Garden. Adam and Eve only saw it from a distance and assumed the worst because their expulsion from the resort had shaken their confidence and given them a form of PTSD.