The torturer has a dysfunctional brain, the kind we call "psychopath," and as such their prefrontal cortex is developmentally damaged.
A torturer whom does so for the sickest possible squirm of pleasure deserves more than euthanasia, yet it is all the good can offer. We leave such fates to God.
Only in a money-nexus world that makes cold emotionality a survival skill can we develop people cold enough to kill via torture.
The torturer imagines himself as some demon of another realm, yet in truth he is a patsy of the devil. We are the heroes who make the heaven upon the earth, we try to save everyone because that is our duty to our creator. However, if anyone gets left behind, if Satan actually gets his way and makes a hell of his own dominion, these evil bastards are at the bottom of our priority list. If anyone gets tortured for eternity, it will be them. That's a promise of sorts, but it's more a function of pragmatism than anything else.
We are all born for love, so how does one become a person so devoid of compassion and empathy that torture becomes even a possibility. The money-nexus world is an atomising world because it forces competition for survival. Have you ever seen how fierce animals become in these situations? And so, in this social-cold-war, with enemies both within nations and internationally competing for survival, we have the environment for the worst possible traits of the human animal to emerge. And, what is more, how can this become part of entertainment? For elements of the subconscious cannot tell the difference between reality and fiction. We stop reacting to the news as real because we wired notions such as torture to feelings of excitement rather than disgust. We are supposed to be protected from such things by developing empathy.