shutdown -h now
or the more recent incantation (from memory)
systemctl shutdown
would be less violent.
AFAIK it can't be stopped either, and at least it sync's and umount's filesystems properly.
Violent is the point-- shutdown might be prohibitively slow. Or it'll get stuck waiting to umount a network share. Or maybe, you want the DRAMs to go dark and start losing ASAP, I don't know. If you must, simply precede 'o' with some sequence of 's', 'e', 'u' so it'll go down hard and fast, but still a bit controlled. I find that 'u' succeeds more often if done after 'e'.
FWIW, this is just what I do with the keyboard (but more slowly) when something went wrong enough that I can't even switch to a text VT and recover. Sometimes even 'b' won't hard reset it-- which indicates everything was already hosed, or maybe just the keyboard. Presumably the umount didn't work either, but I gave it a chance.