Please add php file which can completely delete the extension (files, db tables etc.). File is located here:
[YourMagentoDir] / app / code / community / WP / Amazonimportproducts / wp_amazon_import_products_remove_x.x.x.php

1. Put the file in the root of Magento, where the extension is installed.

2. Retrieve this file through the browser address bar, like this:

3. If successful, it displays "Magento Amazon Products Manager has been removed successfully!"