When the other gods saw the mountain of corpses piled up by Amaterasu, many of them were appalled, horrified, and couldn't even utter a single word from the sheer horror of the sight. It was like gazing upon something alien, something that shouldn't exist or happen. The heads of sixteen Avatars were all lined up neatly on a shrine, a shrine built upon billions of abominable corpses, many of which were strong enough to easily wipe out tens of lesser gods.
Amaterasu was the queen of the gods. They knew she was powerful, but to achieve this without the overgod's authority, no, even with the overgod's authority, such a feat would still be utterly unbelievable.
