Harden transform applies the original resolution of the volume to the resampled volume. If the original resolution was low or highly anisotropic then you may see visible degradation. In this case, probably the simplest is to use Crop volume module with “Interpolated cropping” and “Isotropic spacing” enabled and with a “Spacing scale” that is low enough to preserve all relevant details but still large enough so that you don’t end up with a huge image (something between 0.2-0.8 should work).