Should you want to fully uninstall the app and all it's app blocks or extensions you can follow the steps below
Navigate to your store Settings > Apps and Sales Channels
Click to the right of the app name and click the Uninstall option
Uninstalling the app will remove all the functionality from your checkout immediately if you haven’t already removed the app blocks. If this change is made in your live environment, the app will cease to appear in the checkout or perform any further validations.
No further single transaction app charges will be generated.
⚠️ Uninstalling the app does not cancel the subscription. If you have a subscription for the app you will need to follow the instructions here to make sure this is also cancelled.