Is the Sigma 500mm F5.6 DG DN OS Sports Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 500mm f/5.6 test image. Observe the contrast and resolution of these results.
Is the Sigma 500mm F5.6 DG DN OS Sports Lens set to 500mm f/5.6 sharper than the Tamron 150-500mm f/5-6.7 Di III VC VXD Lens set to 500mm f/6.7? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.