Sharpening is one of those things, that’s so subjective to not only each image, but can be to each part of the image. You have to decide if you want the high frequency detail sharpened, and then to what extent. Then are you applying extra sharpening to the eyes of your subject? Or what about the bark on that tree with the nice texture? To top that all off, is your output for screen, or print? Glossy or Matte?
Lightroom gives us many tools to sharpen our photos, one feature that seems to be ignored sometimes is output sharpening. This option available only in the export panel, is a quick way to apply a final sharpen out output. Given you option for screen, matte and glossy. Of course how much it applies is a bit ambiguous, “low” “standard” or “high”. Well to help out I created this image.
Shot with a Nikon D600, at 1/750 sec ƒ5.6 ISO 400. The raw file was imported into Lightroom the sharpening in Lightroom was set to 0, and no edits were applied to the image, all that has been done has been exported multiple times with each version of sharpening. Make sure you click the image for the full size version to truly see the sharpening.
From this, to me the high of both glossy and matte seems to be a massive jump compared to all the others, with screen being the the softer of all the options.