In reality, he was only half right.
At such a close distance, if it were a Phantom Undead that had achieved Small Accomplishment in Rainbow Light, there is a 99 percent chance it would be completely annihilated.
If it were a Dog Demon or Bat Wing Demon, which had achieved Small Accomplishment in Rainbow Light... there's a high chance they would be severely scorched, and left in a critical condition.
For those of a lower order, such as a Mud-cast demon, unless it's a type with a affinity for Light Element, there's a high chance it would not just be burnt but vaporized
So what happened? Does the Doomsday Messenger · Mo have a bit of resistance towards Light Elements?
It's merely achieved Perfection in its Clay Body and held the Sun Stone in the palm of its hand.
Yet it only paid the price of its arm melting and half its body charring, it could still speak?
"Perhaps, saying 'a bit' is an understatement..."