Is the Nikon 80-400mm f/4.5-5.6D AF VR Nikkor Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 300mm f/16.0 test image. Observe the contrast and resolution of these results.
Is the Nikon 80-400mm f/4.5-5.6D AF VR Nikkor Lens set to 300mm f/16.0 sharper than the Sigma 150-500mm f/5-6.3 DG OS HSM Lens set to 500mm f/6.3? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.