Is the Canon EF 70-200mm f/2.8L IS III USM Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 70mm f/4.0 test image. Observe the contrast and resolution of these results.
Is the Canon EF 70-200mm f/2.8L IS III USM Lens set to 70mm f/4.0 sharper than the Canon EF-S 18-200mm f/3.5-5.6 IS Lens set to 80mm f/5.6? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.