To completely remove a Web Part from SharePoint (and not just uninstall it) you must follow the instructions below:
Go to Site contents of your root Site Collection and click on Style Library;
Search for BT WebParts Add-ins and open the folder;
- Select the Web Part(s) that you intend to remove;
Click on the option to Delete.
The BindTuning Web Part(s) files had been removed from the site.