First, log in to your https://www.onlineconvert.com account using your username and password.
On the account settings page, look for the Delete Account option.
Once you find the delete option, you may be asked to confirm this action, as once an account is deleted, all data and information associated with it (including conversion history, preferences, etc.) may not be recovered.
After confirming the deletion, you may be asked to enter your password or go through other authentication steps to ensure that it is you.