This program doesn't meet my needs and is generally clunky. How do I get rid of it?
Do you want to remove your account or delete an extension?
For Firefox extension, click on the orange Firefox button, click on Addons, then Extensions on the left side, and click Remove beside Todoist.
For your account, sign into it on the web version, click the gear icon in the top right, Settings. Under Account, there will be a a Delete My Account link.