He overpowered Ultra Tiger Hunt and sent Zoro flying out of the Skulldome with a named attack.
Tempura Udon did this.
It quite literally uprooted a part of a mountain range [as Law described it] from the bedrock and up.
If you want to see the size of that mountain range here ya go:
A number walked through this door and the mountain on the roof is 3x/4x the size of a number (~ oars so approx. 50 mts give or take).
The mountains downstairs dwarf the mountains on the rooftop.
Moreover Tempura Udon is a piercing attack, unlike Boundman's blunt force attacks so there's the added lethality factor as well.