I don't know if your phone it's rooted or if you know terminal but rm
it is a badass delete command even in Linux it is really hard to get information from, deleted whit rm
but not impossible if you want to don't have to factory reset your phone for delete something you can over write on it, like delete it whit
rm -rf myfolder/to/delete
okay and then over write the space left on the device like
dd if=/dev/zero of=/sdcard/some_file_name.txt bs=1024 MiB=space_left_on_megabites
this will create a file of the size of the space left on where you want to overwrite the sd or the internal storage you must be really carefully whit the dd
command "space_left_on_megabites" it is the amount of megabytes left on the device if you have 6 gb it must be MiB=6000 etc..
you will get the notification of running out of space on the device don't worry you would get it back
ones the dd
command finish it will take some time it's writing whit zeros on all the space left, then you delete the /sdcard/some_file_name.txt whit rm
rm -rf /sdcard/some_file_name.txt
then you have wipe ones you available space if you what to make it harder you must repeat the process like 5 times and then it will be really really impossible to recover it! but whit one time does app you mention it wont be available to get it back