The process of deleting your facebook profile is definitely not straightforward. It may even be quite appropriate to call the entire process involved to delete a fb profile as tricky, confusing, frustrating and misleading.
Deactivating your account isn't going to delete all your stuff permanently. It only puts your account on a temporary hiatus, during which your profile and other content related to it, isn't shown to anyone, including your friends. The moment you log back, everything related to your account (friends, photos, comments, likes, groups etc) gets restored to how it was before you chose to deactivate it.
If you want to permanently delete your facebook account forever, go to this link:
After you complete and submit the deletion form, your account will be in a deactivation mode for 2 weeks.
During the immediate two weeks after submission of your deletion request, don't use facebook in anyway using the login credentials of the concerned account.
After two weeks, according to Facebook's policies, your account should be deleted permanently. At the point, there is no way to restore your profile back, and all your profile related content is permanently deleted from facebook servers.
To confirm, just try logging-in using your deleted account credentials. The login attempt should fail, prompting an error. This login error positively confirms the deletion of your Facebook profile for good, at least according to Facebook's own account deletion instructions.
To be safe, try the above step at least 15 days after you have submitted the request for deletion.