How can I delete this account?
in order to permanently delete your Todoist account and all data associated with it, please log into your account, go to Preferences (gear icon in the upper-right corner) -> Account and use the "Delete my account" link at the bottom.
I tried that, but it won't allow me to delete. It keeps telling me I have the wrong password when I am using the very same password that I logged in with.
If you have used the GMail Login method to set up your account, please go to https://todoist.com click on the gear icon in the top-right corner to enter Settings -> Account and here, you must first use "Edit" in the "Password" section to set a password for Todoist and then use the link at the bottom to delete your account confirming with the newly set password.