[Samsung Galaxy S7 Edge Questions and Answers] ableright:
I don't know that I can be of help to any one person here, but I have gone through a long recent experience with this. I think a lot of people (including myself) are confused about bootloading. I think there are many members here who are not, and I might still be confused. If I'm wrong about anything I'm saying here please correct me with facts. The way to fix a hard bricked phone is generally flash the BIOS back, but that can be a catch-22 since you can't get into download mode to flash a stock ROM, but not always which I'll explain.

I do Software/Web Development I know C C++ C# and higher level languages, so I'm decently knowledgeable about computers in general. That said, I'm not deeply intimate with extreme low level issues which hard bricking phones revolves around, however I think I have a rudimentary knowledge of computer booting processes. Firstly, my story of how I bricked my own phone.

I bought on LG G4 (about a year ago). I toyed around with it of course and TOTALLY MY FAULT didn't read something carefully on a ROM and flashed an INCORRECT ROM. This overwrote the bootloader and the BIOS I'm sure. The screen was literally dead and I mean dead. Nothing would show except a little light, but literally no data on the screen NOTHING. I thought for sure I had a dead phone unless I wanted to buy a JTAG box that you hook up to the phone with wires and it rewrites the BIOS.

The thing is the box was 100 dollars and I paid 100 dollars for this phone used, so what was the point? I thought I would keep the phone around just in case someone had one, and yes that WOULD likely fix the phone, but it's the harder option and I'll explain how I fixed it here in a minute. So firstly, I think some people are confused and again people can correct me if I'm wrong, but the Bootloader and BIOS or Boot Rom as I believe it's called on phones are Not the same.

It's important that people understand that distinction. So the process goes something like this in all computers

BIOS->loads the most basic starting points for the device, it contains the very first code which is executed by the processor on power which also tells the machine like a road map where the BOOTLOADER is. The bootloader at that point loads the Firmware/drivers that make the device/phone work for the hard drive etc. What happens if there's no starting point though and the BIOS is gone? You get a hard bricked device that shows literally nothing on the screen.

That's the difference. So how did I fix my phone? Thankfully, this day in age even a messed up BIOS isn't always doom, and it seems to be getting safer/better with time. It appears for example on my LG G4 the phone can be bootable with a BIOS and image install or written to an SDCARD. With U-Boot on Android developers can boot from an sdcard like a completely different BIOS and bootloader, but it looks like on the G4 if it can't boot from the main BIOS it will automatically check the sd card for BIOS and a bootloader option.

It's just one of those weird things. A few days ago I decided to see if anyone had come up with a hard brick solution to the G4 with Googling around, and sure enough someone had a stock image to write and boot via the sdcard. This is after months of thinking it was doomed on my end. I ended up using Win32DiskImager to write the RAW to the sdcard and after booting from the sdcard image I could go into download mode. Once in download mode I could write the entire stock .kdz image to the phone which writes literally everything back to the phone the recovery and yes EVEN THE BIOS it appears. So if I'm understanding things correctly I essentially:

->Booted a BIOS and stock image form sdcard on the sdcard which the phone is designed to be able to boot into sometimes.

->Download Mode allowed rewriting the KDZ which contains the BIOS and that is overwritten back to the way it was

->Phone boots without SD card as always. Fixed!

So my point is some of you shouldn't necessarily give up. There likely is the option of using a JTAG box wired to the phone, or even someone that has created a stock recovery image that might BOOT from the sdcard. There likely IS a way to fix most of these hard bricked phones since at the end of the day it's usually a software issue at the lowest level I.E. the BIOS, and the phone has no road map to the bootloader and further drivers/firmware.

I hope this helps, and I hope if I stated anything wrong in my reasoning and information above that someone corrects me. Peace and Good Luck!