Is the Sigma 150-600mm f/5-6.3 DG OS HSM Sports Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 1200mm f/13.0 test image. Observe the contrast and resolution of these results.
Is the Sigma 150-600mm f/5-6.3 DG OS HSM Sports Lens set to 1200mm f/13.0 sharper than the Sigma 150-600mm f/5-6.3 DG OS HSM C Lens set to 840mm f/10.0? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.