Unique? I specifically used the word mostly and not unique. And the scale is vastly different. Also "killing" was just an over-encompassing metaphor.

I'm not implying that needless killing is the only, or the main thing that sets us apart from animals, except in the context of the comment I was replying to (about lions feeding on an impala). But it's taking this kind of actions despite having the ability to be aware consequences that makes us special. You would expect the threshold for some of these actions to increase with these newfound abilities but it went the other way around. A person is willing to kill a last member of a species not for survival but for little more than a trophy on a wall.

There are probably far more things that set us apart from animals than instinct or awareness of consequence. Most children actually lack these abilities because they are partly taught, they have to be groomed. So the main difference might be that we are able to learn up to a point that no animal can rival us. This is the perfect example of what a human can be without "learning": https://en.wikipedia.org/wiki/Oxana_Malaya