[Galaxy S6 Edge+ Q&A, Help & Troubleshooting] Talysdaddy:
You've never stated the results of your stock firmware flashing, using Odin. This is key, this tells you whether the firmware was flashed correctly or not.. If you picked the wrong stock firmware to flash, Odin will show it "Failed."

If your buddy just updated firmware, then it's likely he's on the newest one, but check in SamMobile to verify if it's accurate. If shows the most current firmware was updated in January or something then he might not be on the most current one, as this shows that he's behind on updating his phone, so it's uncertain which it last updated to.

If I were you, I'd verify first whether the Odin flash passed or not, prior to attempting any custom flashing.. After Odins finished flashing in the upper right corner will either show "Pass" or "Fail," it needs to show "Pass" before you can proceed to do anything else, as this confirm whether the stock firmware flashed correctly or not.

If it doesn't Pass, you have flashed the wrong firmware. Might be good to verify with your buddy, which carrier he had originally. If you indeed have a Samsung S6 Edge+, with the larger 5.7 inch screen, the model numbers begin as so, "SM-G928x" with difference being the "x" at the end, which coincides with whichever carrier it's on, (e.g. "A" for AT&T, "T" for T-Mobile" - U.S. carriers).

It wouldn't be a bad idea to confirm whether you're using the most up to date version of Odin, either. Don't remember what that is but a quick Google search under this topic would do it.

Just for shyts and giggles, you did verify that your PC recognizes the phone, right? And that it lists under "Device Manager" correctly, as well as Odin recognizing it after you plugged it in?

If it does "Pass," it should reboot by itself into the stock firmware since prior to flashing you selected "autoreboot" and "reset time" if it doesn't reboot correctly or gets stuck on the splash screen, unplug it from the PC and manually boot it into stock recovery. Do this by first pressing the following buttons at the same time and holding them till the phone powers off, power button, home button, volume up and volume down.. After it powers off, push and hold, power button, home button and volume up, till the phone boot to stock recovery, amd of course you can let go of the buttons/keys. Then using volume buttons to select factory reset and pressing the power button to confirm the selection. After it factory resets you can then select reboot to system and it should boot normally and you've recovered the phone.

The upper left corner in Odin will show the results of the flash, there shouldn't be a reason for it not booting if it indeed shows "Pass," cuz this confirms firmware flashed correctly, if it shows "Fail" then you flashed the incorrect firmware. You'll need to locate the right one so that Odin shows "Pass," otherwise you wont ever recover your phone, regardless of anything else you find interesting to flash, bootloaders, TWRP, root, ect.. Don't flash anything else till you get the stock firmware flashed correctly. If you're unable to accomplish this then, I'd recommend calling Samsung or your carrier, is it still under warranty? My charging port broke after 2+ years, I have insurance though w/ T-Mobile, called them to see what my options were, was planning on fixing it myself to avoid the $175 insurance deductible, if I made a claim, but as it turns out, since I have insurance, the phones still under warranty and per the CSR, it will continue to hace warranty as long as I pay the $7/month insurance. Thought most warranties are 12 months but I wasn't going to correct her if she was wrong so I went ahead with it and 2 days later new phone came and I sent my broken one back! Old phone has lil scratches on the screen, couple lil dings along the sides, obviously an older phone but now I gotta new one, ita flawless!

It won't to try if this don't work out..

Good luck