Currently, blocking a group on WhatsApp is not an option. However, you can leave the group and block the admin instead.
Additionally, you have the option to report a group. For detailed instructions, refer to this article.
You can control who can add you to groups by adjusting your group privacy settings.
Block an admin not saved in your phone’s address book
Click the WhatsApp group chat, then click the group subject.
Under Group info, click the admin you want to block.
Click Block {phone number} > Block.
Block an admin saved in your phone’s address book
Click Settings (gear) > Privacy > Blocked contacts.
Click Add blocked contact and enter the contact name.
Click the name to block the contact.
