Account deletion/permanent deactivation?

It seems like the profile settings have no way of deleting an account, or irreversibly disabling the login for the future to prevent malicious overtaking of a definitely abandoned account. Or am I just missing it? I couldn’t find it. I definitely do not want to use this account anymore, and the e-mail associated with it may soon be available to others, so it’s not really safe to leave the account in a normal usable state.