Years ago I read a book about computer viruses and the one that caught my attention the most was the Turkey Virus which could actually kill hardware.
One variant of the virus would focus the beam in a CRT monitor such that it would burn it out. By burn it, I don’t just mean phosphor burn-in, although that was a side-effect, but the electron gun would fail, leaving the monitor completely dead.
Another variant of the virus would perform mathematical calculations in such a way that it would overload the co-processor and cause it to burn out.
Of course this was some time ago in the days of older hardware that was susceptible to this sort of attack. Thankfully, modern hardware is generally designed to prevent it, but that’s probably not going to stop someone who is determined enough.
Also, it would be relatively easy for a virus to kill the BIOS. There’s a reason that BIOS flashers always warn you not to turn off or reset the system during the flashing; it’s because an incomplete write would leave the BIOS corrupted, and since the BIOS is the Basic Input Output System of the computer, corrupting it would render the system inoperable. Once upon a time, the BIOS could only be flashed from pure DOS mode, but Windows flashers have existed for some time. There is nothing stopping a virus from writing some bad stuff to the BIOS and thus killing the system. CIH / Chernobyl did exactly this in 1999.
Luckily, some motherboards come with dual BIOSes so that the backup can be used in case of corruption of the primary, and others make it possible to reset or re-flash a corrupt BIOS, but not all do or can.