Board Thread:General Discussion/@comment-27174095-20171114023949/@comment-27174095-20171128122514

The narrator in part 2 pretty much explains that pure Hamon only effects humans like strong sunlight; it gives them pins and needles but with overexposure can cause them to faint. If using Hamon on the World could've harmed Dio, then it stands to reason that using it on Empress would've had the same effect on Nena as Hamon on a normal human. So maybe Joseph was trying to make Nena faint, which would cause Empress to "deactivate" like stands do when the user is unconsious.

But I guess that's just my headcanon.