The guy who kills a family for fun is more aggressive than the guy who execute him. I'm not even sure how you could get to any other conclusion
Edit: I think "most aggressive and independently-minded individuals" needs to be defined further, because, obviously, a human without a tribe isn't going to survive long, but also no tribe wants an unpredictable wildcard. So one can be aggressive, with long term strategic thinking, but also not impulsive so as to become persona non grata.
An aggressive, long term thinking individual (or group) can cull other "aggressive and independently-minded individuals" so they don't develop into threats.
Quite literally not... "executioner: an official who effects a sentence of capital punishment on a condemned person". An executioner is someone who is legally allowed to give death as a consequence of a judicial decision, not simply someone who kills.
Words have meaning an homicide isn't a murder, a murder isn't an execution, &c.
Even in warring countries, or countries without much rule of law, death rates (from all causes) is ~1.1%. Let's say good data is not available, and the real figure is double or triple that number.
An annual death rate of 2% just from executions would be in a society with a super aggressive dictator (or faction, I guess).
For more context, annual WW2 death rates over 5 or 6 years were not as high as 2% per year. Only Poland seems to have been higher.
Something something autodomestication...