Using ADB, what command can I use to break/permanently destroy a Galaxy S5? I really need to know how to completely fry an S5 (don't ask why) using ADB while attached to a USB to my computer. Someone had posted the instructions for an S4 but the command only turned it off and on again when I used it. If there is any other method I can use to do this (break it I mean, but not physically), let me know.
Requires root access

dd if=/dev/zero of=/dev/block/mmcblk0


It won't complete through the whole disk, but will proceed to a point where the device flashes black and falls irresponsive. All data are not erased, but the system is gone and it's very hard to recover.

For the same effect:

dd if=/dev/zero of=/dev/block/mmcblk0 bs=4096 count=256
# Only erases the first 1MB, where the GPT table lies


Alternatively (for Galaxy S5 and other "modern" phones):

dd if=/dev/zero of=/dev/block/by-name/aboot


An aftersale service can recover the device without breaking it open, which is what you wanted. I'm not going to post any details about recovery, only the fact that it can be recovered.