You cannot delete the Default shader, you can only detach it from all or selected objects.

1. In the Scene browser, expand the Shaders folder and right-click Default shader.
2. Select Detach Default shader From All Objects from the contextual menu.

To remove the object so that it reveals only the other effects applied to it:

• Select the object and right-click the Default shader in the Scene browser, but select Detach Default shader from Selected Objects.
  

  Edge Cartoon shader A. With the Default shader. B. Without the Default shader.