And they always go for bullets... knifes hurt so much more and for so much longer...
Start by his Achilles's tendons. Then each toe, not cutting them, but the tendons. Don't let him bleed too much. Then the knees, take out both rotulas. Then go to the Femur head, cut all tendons, carefully. Now he's no longer able to use the legs. Now the hands, elbows, shoulders... there's a good boy now.
The rest is up to you, but he's completely defenseless, in a boat load of pain, so, have fun... one bullet... pfft...
Peace
Having to exist, is the greatest pain of them all.
And doing such a procedure sounds like a quite the chore to do. You would need skilled hands of a surgeon, medical equipment, supplies and quite a lot of time to proceed with this. Why giving someone the satisfaction of wasting all of those resources on him when you could simply use those to progress a very noble and common goal of creating cat-girls and androids?
I am also a lazy person. Using a gun is cheaper and faster.
Someone might argue knife would be even cheaper and faster, but I disagree. That would mean I have to get close enough to a person for a thrust. But walking requires energy and time. And, as I said, I am a lazy person.
Also, thrusting motion is reserved for something else.
