If you wish to remove WP Statistics, you can do so using the standard WordPress tools, however WP Statistics will NOT delete the statistical data or settings from the database using this method.

You can remove the data and settings by going in to the Statistics -> Settings -> Removal tab and checking the “Remove data and settings” option. This will delete all tables and settings and effectively disable the plugin.

You can then go to WordPress plugins page and disable/delete it completely from your site.