Delete a user group
Select the site, open Members → User Groups, and open the custom group. Review its members and access before choosing the delete action and confirming.
Deleting a user group removes that group as a way to receive shared access. It does not delete the people's organization accounts or remove access they receive through other groups.
Protected default groups cannot be deleted. If the goal is to remove a person from a site or revoke a management role, use the membership or role controls instead.