BOOM! BOOM! BOOM!
Tiamat's Death Authority was just as powerful in the Heavenly World as it was in the lower universe.
Along with Iris, Tiamat was one of the strongest people in Grand Heavens Boundary. They may have come to a place where stronger people existed, sure, but that didn't discount the amount of time they spent growing and training.
They were already high-rank Demigods. They'd been at that level for thousands of years, unable to progress much further because they were near the ceiling of their current power level.
Tiamat was a top powerhouse even in the Heavenly World. Perhaps she couldn't have the level of authority a God could hold, but under that level?
She was practically unparalleled.
The enemy vanguard completely collapsed because of her interference.
Grunts were durable. They didn't have much power, but their bodies could take hits like no other.