You can delete a group for all group participants if you’re the group admin. Before you can delete a group you must remove all group participants, and then exit the group.
When you delete a group, you’ll no longer see the group in your chats list and the chat history will be erased from your phone. Other participants will still see the group in their chats list. However, no one will be able to send messages.
In order to delete a group, you first need to exit the group.
After you exit a group, you have the option to delete the group.