How to "really" delete whatsapp images that were already deleted? I've deleted around 800 images from WhatsApp folder using Google's Photos app, but the problem is no space was free'd at all, I'm guessing those images are still available at /sdcard/WhatsApp/Media/WhatsApp Images.

Is there a way to delete those 800 "original photos" without having to manually select them again?

I'm using Motorola Moto X Play, Android 6.0.1, no sd card at all.  

PS: I have Google Photos backup disabled even before that event.
If you are deleting all the images in the directory, just delete the directory. If not, unfortunately Google Photos is a backup and unless you have it enabled to delete backed up photos off your device, I don't believe there is a way to mirror the deletions.