In order to uninstall Quack from HubSpot you have to navigate your way to your connected apps within the settings of your HubSpot account.
When you have done that, you can click the drop down near the Quack logo that will appear in your connected app list, and from their you will see a button that is titled "uninstall" and from there you can work through the steps of removing the Quack app.
If you'd like Quack to delete your corresponding data, reach out to our support team in the platform and we'll happily help out with this!