There was a way you could burn out a chip in the C64 with a poke command IIRC. And you could break the tape advance relay in the MSX by switching it on and off rapidly.
It's much harder with early 80s hardware (and no internet to learn this stuff) than with modern hardware. These machines were stateless beasts. You could either damage the BIOS with writing to it somehow, or fry some hardware. I suppose you could damage the floppy drive head with very intensive seek commands in a tight loop, or something like that.
I managed to kill one PC floppy drive by switching the motor that rotated the disk and not switching it off (because my crash handling was nonexistent and floppy read routine I was writing crashed somehow). I guess the disk rotation motor (or its switching circuitry) overheated (after all, it was supposed to be used with a reasonably low duty cycle): the drive would no longer rotate the floppy (so I could also not tell if the rest of the drive still worked).
Oh the MSX had it too for sure.. The TRS-80 was almost not sold here in Europe. We had some Radio Shack shops (called Tandy) here but the TRS-80 wasn't a big thing. We only got the LCD model.
But it was exactly the same thing yeah.. Jiggling the relay super fast would fuse it. One of my friends had this happen to his MSX 1, I think there was some early 'malware' in a copied game or something. But at least a relay replacement is not difficult or expensive.
Edit: Oops it wasn't the 64 but the PET: https://dfarq.homeip.net/the-killer-poke-for-the-commodore-p...
Also, everyone here will know the phenomenon of bricking. You can damage hardware with software. Luckily it's very rare.