How do I Delete all WhatsApp photos from my iPhone
To delete all WhatsApp photos from your iPhone:
Delete all photos in the WhatsApp album of your Photos app (make sure to delete them from the Recently Deleted album as well).
Open WhatsApp > Settings > Storage and Data > Manage Storage. Go through every single conversation you have under CHATS and delete your photos one by one. You can also delete all your videos from WhatsApp from this menu.