When he landed his hit, he wielded only one scythe, meaning that he had to put the other back in his back to switch a stance, which is fundamentally different from the way Killer fight normally. He was able to swtich between the two/one sycthe style before, but when he went for the kill, he could only do so with one at a time, meaning that his stance was fundamentally different from what it was usually.
and secondly u know what this chapter proved our points u said that scythes are just a nerf for him and he couldn't bring his full power now let's analyse this :
now where is this headcanon of him not being proficient in using scythes ? 

i don't know luffy had kaido bleeding / law / killer but i didn't see Kid 