Is the Sony FE 90mm F2.8 Macro G OSS Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 90mm f/4.0 test image. Observe the contrast and resolution of these results.
Is the Sony FE 90mm F2.8 Macro G OSS Lens set to 90mm f/4.0 sharper than the Sigma 70mm f/2.8 DG Macro Art Lens set to 98mm f/5.6? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.