Managers can only delete unconfirmed users who haven’t yet confirmed their accounts. Once a user is confirmed, their account can only be disabled.
To delete an unconfirmed user, click the Users & Groups tab in the left-hand menu.
Search for the unconfirmed user you want to delete, and hover. To the right, you will see a trash can icon appear.
Click the Trash icon and confirm that you want to delete the user by typing DELETE and selecting Confirm.
If you would like to disable a user's access you can do so by clicking the blue toggle in the "Enabled" column. Toggled to the right and blue means the user is enabled, and toggled to the left and gray means a user is disabled.
A confirmed user cannot be deleted from the Users page because their activity remains tracked in the History of the videos they viewed or managed.