How do you delete the ACTUAL contact? As the topic title suggests.
Apart from @Gary has already advised above about deleting email address suggestions and disabling the sent folder for suggestions in Settings, to “find and delete the contact from your account address book” do the following.
1). To remove that unwanted email address from your Contacts, when you compose the email, "Click on the word “To” (on the left) as in the example below.
2). Then “Click the dropdown on the far right of Folders” and select “All Contacts”.
3). Then either “Type the unwanted email address in the Filter Contacts field” and enter, or Scroll down and find the unwanted email address".
4). Lastly “Right click on the unwanted email address” and delete it. Then “close the select contacts window and close the compose window”. Then open a new email and it should be gone.