Here are three possible options that come to my mind:

• sharpen the image before downsizing

• cut out the most important part of the image

• downsize 50% several times instead of resizing once

Downsizing ultimately means that you loose information. You can only try to achieve a "good" result.

Here are three possible options that come to my mind:

• sharpen the image before downsizing

• cut out the most important part of the image

• downsize 50% several times instead of resizing once