Is the Canon RF 14-35mm F4 L IS USM Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 35mm f/11.0 test image. Observe the contrast and resolution of these results.
Is the Canon RF 14-35mm F4 L IS USM Lens set to 35mm f/11.0 sharper than the Sigma 14-24mm f/2.8 DG HSM Art Lens set to 14mm f/2.8? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.