People actually not get it how op Law attack was and what Law sacrifice to hold the damage low as possible for not destroying Onigashima and a large part of Wano.
First he stab BM:
So after reaching Wano ground, Law could used his attack, but the outcome of the attack would destroy the whole area, he would destroy more as what he did in current chapter, the area would fall in dust, he couldn´t used it since he would destroy large area of Wano. So he go thought the ground more and more, risking CoA punches of Bigmom!!
And when he was deep enough, he release the insane power of his sword who was still to broken:
And the result of all this, here step by step:
Law make such a big hole, that multiple mountains together couldn´t even fill it!!
The hole is soo deep that we can´t even see the ending from above, meaning Law really put anything to make the damage on Wano not bigger as it is.
Then you see the smoke, covering mountains and even Onigashima, make them looking small, same smoke is from Momo perspective nothing to the big hole.
What Law did here was beyond a normal island lvl attack, if he would directly used it, it would not just destroy Onigashima, probably even part of Wanokuni.
This feat is one of the most op feat which we see a while in One piece since Whitebeard, imagine if Law wouldn´t go throught sooo deep to reduce the aoe damage, perhaps the attack would destroy Onigashima+Flower capital area in a insane powerfull shockwave.
Mountains even look tiny compare to the big hole.
I most like see when a calc later come out, the feat is moving around island-small country lvl.
That was really a insane feat, insane how BM tank it soo far.
Law really got insane feats this arc in general.