In order to view all access provided to 3rd Party applications, you have to log in to your Amazon account(amazon.com). From the “Account and lists” dropdown, you should navigate to ‘Your Account.
In “Your Account”, you will see a section called “Other Programs” from which you will be able to manage your logins. Click on “Login with Amazon”.
Here, you will see all the applications you have provided API access to in the past. Find the application for which you would like to remove access and click on the remove button.