Is the Canon EF 16-35mm f/2.8L III USM Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 28mm f/4.0 test image. Observe the contrast and resolution of these results.
Is the Canon EF 16-35mm f/2.8L III USM Lens set to 28mm f/4.0 sharper than the Canon TS-E 17mm f/4L Tilt-Shift Lens set to -12mm f/4.5? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.