Durability?: Rendered obsolete as 自分 transcends it
Size?: Rendered obsolete as 自分 transcends it
Causality?: Rendered obsolete as 自分 transcends it
Imagine the concept of reality itself as a piece of paper
Now imagine 相手 as an inhabitant of this paper
To 自分, lesser beings bound to such concepts like dimensions & spacetime's nothing more than a doodle on some piece of paper
& using his blade, he cuts not just 相手, but their very reality/canvas & archē
So ultimately, while 相手's impressive, he simply remains unassailable & utterly unaffected