User groups can be deleted by selecting the relevant group in the Groups panel. To do this go to "Manage>Users and Groups" then select the group you wish to remove. In the top right of the main panel select the “Actions” drop down menu. Click the “DELETE” button in the dialogue box that appears select the “REMOVE” button to confirm.
Deleting a group does not delete its users. Your users can still be found in the default group: All users.
Users of the deleted group will no longer be able to access courses made available to them via that group. However, course results from historical attempts will still be available to account owners from the course reports page.