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I just want to delete all of them.

Just go into the camera roll and select a picture then delete it with the little trash can icon for each one.

If you are using a Mac as your computer then attach your iPhone and open Image Capture and in the Options tab tick the 'Delete items from camera after downloading' option and then download them.
 
If you have a PC, and hook up the phone, and use Windows Explorer to browse the phone, can you just delete them all there?

Probably so, but I just haven't tried it yet.
 
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