If you took Zoro’s katanas away and gave him 3 standard pirate swords, is he nerfed? In my opinion, the answer is yes. Zoro’s 3 katanas are of a much higher caliber than your standard pirate sword, and therefore Zoro with his 3 katanas is going to be stronger than Zoro if he were to be fighting with 3 run of the mill swords. Sure any blade can become a black blade, but Mihawk with Yoru is going to mid diff Mihawk with Bastille’s sword lol.
However, Even if we agree on the above, with Killer, this analogy falls flat for 2 reasons:
1. We don’t know if Killer’s wrist scythes are stronger than the scythes he got from Orochi. Orochi’s scythes could very well be very high quality weapons assuming they were made in Wano which has had a history for high caliber sword smiths, and thus they could be superior weapons to his standard wrist scythes.
2. Killer’s wrist scythes and Kamazou’s Wano scythes are fundamentally different weapons. Unlike the Zoro analogy where Zoro is just switching his katanas for 3 weaker versions of the same weapon, Killed is picking up different weapons from the ones he seems to prefer using. This doesn’t mean that Killer is weaker with Wano scythes than he is with the wrist scythes, but at the very least he seems to like his wrist scythes better.
So really any opinion is valid here and we need more information to say, but I would argue that he was at least slightly nerfed, as like I said above he does seem to prefer his wrist scythes to his Wano ones, and I think that is going to be the difference maker tbh.
So I vote for slightly nerfed.