Is the Tamron 18-400mm f/3.5-6.3 Di II VC HLD Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 200mm f/6.3 test image. Observe the contrast and resolution of these results.
Is the Tamron 18-400mm f/3.5-6.3 Di II VC HLD Lens set to 200mm f/6.3 sharper than the Canon EF-S 18-135mm f/3.5-5.6 IS STM Lens set to 135mm f/8.0? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.