The default security group is named default and cannot be deleted.
If you want to delete a security group that is associated with instances, such as cloud servers, containers, and databases, you need to remove the instances from the security group first.
A security group cannot be deleted if it is used as the source or destination of a rule in another security group.
You need to delete or modify the rule first and delete the security group.
For example, if the source of a rule in security group sg-B is set to sg-A, you need to delete or modify the rule in sg-B before deleting sg-A.