The Samsung Galaxy S7 and likely other Samsung phones can be booted into safe mode with the volume down button.
However, if you damaged and bent your phone at the button like I did, you might end up with a situation where you can't get out of it. Oddly, in normal use, the button is non-functional. If I hit volume up, it doesn't go down on its down, so it's not stuck. Despite that, the boot process sensed something wrong, so it just be some kind of short.
I did manage to get it to boot normally, though. I just pushed as hard as I could to straighten the phone back out as it booted. I'm a wizard, Harry. Hope this helps someone.