You can delete from iPhone by the simple steps:
Step 1Click the “Photos” icon on your iPhone’s home screen. The Photos icon has a yellow flower on it.
Step 2Click your Camera Roll to view its contents.
Step 3Click the “Share” button in the top corner of your iPhone's screen. The Share button looks like a rectangle with an arrow pointing out of it.
Step 4Tap the thumbnail image for each of the photos you want to delete.
Step 5Tap the “Delete” button to
remove photos from iPhone’s Camera Roll.
If it doesn't work, you can have a try an
iPhone Data Eraser with a free trail. It is compatible to all iDevices.