If you have Fire Aspect on a Sword along with any enchantment that can kill a player in one strike, when you kill the player a small flame from the fire aspect will apear in mid air.

ARMOR MUST NOT BE WORN
Get Fire Aspect 2 on your sword. Get Sharpness 5 on your sword. Deliver a Critical Hit and kill the player.

When the player's death animation is over a flame with be floating in midair.

I expected the flame not to be there.