Only too true... I have not seen any of the ones you describe.
I didn't try and say they don't exist, only that I had never seen one I'd be willing to own
and perhaps defend my life with. And I
would believe the edge you can put on your
fixed blade knife, because I own one.
The two shivs I pictured above have been with me for a very long time. I bought the Buck knife
in the '70s, and my friend John made the other one for me in the eighties. I've field dressed many
deer with them, but never threatened a human with one. I'm just not wired that way. If someone
pushed me far enough that I drew my knife, it would be for keeps. Me or him.
I can testify that the fixed blade knife and the buck knife above both have handles that don't
slip easily, even if they are covered in blood, and the weather is so cold that your fingers begin to lose feeling.
I've always feared those blades, and feared to lose control of them
when slippery or very very cold. But my hands have managed to keep their grip on those
handles while I did necessary surgery while holding a flashlight in my mouth. That says
worlds, in the north country deer woods.
For my part, my idea of a fighting knife is the one issued by the U.S. Marine Corps. Which answers
the OP's question. Salut! Sergio... This is the K-Bar knife. When it's down to mano a mano...
View attachment 13240
No mechanism, nothing tricky, just a very strong blade with a guard to protect the fingers.
Keep it simple when your life depends on it. Just my opinion.
If any knife could punch through body armor, it might be the K-Bar.