Performing a factory reset can help delete all data on your device, but actually these data are not wiped completely. Instead, you can recover them easily by many kinds of recovery tool. So now, Android data eraser
may be what you immediately need. It can completely and permanently delete all your Android files, and it supports nearly all of the Android devices. You can read this tutorial, how to wipe Android phone
, to learn the quick way of wiping Android phone. Hope it helps.