Have you signed up with the wrong email address and you need to delete an old account? It's as simple as going to your Profile and account menu and clicking a button (and solving a math question to avoid unfortunate mistakes 😄 )
Please note that you will lose action to the account and all its data. There is also one restriction to deleting accounts. If you are a non-administrator member of at least one organization, you cannot delete your account. In this scenario, you need to ask the admins of said organizations to first remove you from those.