I figured unarmed meant bare hands, bionic claws makes it much easier. It may not be literally impossible, but you are likely to require both massive stats, eight tentacle arms, and possibly one of the claw mutations.
Vorpal is any cutting weapon that you go through the right process with. I believe you can find it on the wiki, not sure if I should spoil it here. Also cata++ mod has vorpal as part of its added martial art, which I removed after I cut someone’s head off with my hands, even if my char should be able to do that.
(Edit) Alternatively, I might be an idiot. Forgot I was wearing two of everything. There is an immense difference between 12 moves to attack and 160 moves to attack. I R DUM
