When deleting your account, consider the apps that you've linked to your Facebook account.
If one of them logs you in to Facebook it will cancel the account deletion process. So,
When you delete your Facebook account this will not delete data that has been shared with apps.
‘When you use an application, the application may ask for your permission to access your content and information as well as content and information that others have shared with you. We require applications to respect your privacy, and your agreement with that application will control how the application can use, store, and transfer that content and information.’ — Statement of Rights and Responsibilities (Facebook)