That's literally Chinjao's strongest attack mate. If you're gonna mock someone, at least try doing it in such a way that it doesn't make you look bad.
The point isn't about just cutting a mountain. I know what it means to send Oden flying, but that's beside the point. Unlike Law or Zoro, Mihawk ended up cutting a mountain-sized construction unintentionally. He was attacking a scrub and he never intended to cut the ice mountain, but the byproduct of his attack ended up destroying the ice mountain that's nowhere near him. His attack was more powerful and destructive than Roger's attack despite him putting in less effort. Yeah I know it's not one of Roger's high end moves, but I doubt Mihawk used a high end move to kills Luffy.
Roger's only saving grace is that it was a one-handed slash.
I doubt the attack that cut iceberg was stronger than an attack that send far away someone like Oden who was full onguard.
Likewise the attack by Mihawk was powerful enough to cut iceberg from far away. But we don't know if that attack could overpower someone very strong, that's why scaling icerberg vs Oden is different story.
It's just like comparing Zoro billion fold and Ashura. Billion fold is a large scale that cut giant stone Pica meanhwile Ashura is small scale attack but stronger.
To be more clear the slash send by Mihawk to measure Whitebeard should be stronger than the one that cuts iceberg. But guess what Jozu block it.
Hitting a stationery object like iceberg and hitting a strong individual (who can block and resistis with their own strength) is very different.
So i doubt Mihawk slash iceberg was stronger than Kamusari. So my point is Kamusari will not cut iceberg from that distance like Mihawk, but it is alot more powerful.