The classical Roman punishment of decimation did not just mean executing every tenth man.
It meant every group of ten men in a particular cohort or legion would draw lots, and then the nine “lucky” ones would have to beat the loser, their compadre, to death with clubs.
A lot more traumatic to the survivors, I would think, than having outsiders execute one in ten of your cohort.
BTW, it was fairly common under the early Republic, but had become quite rare by the late Republic. If I remember correctly Crassus used it at least once against units that had fled from Spartacus.
Genghis Khan was a bit more ruthless with his methods, he invented “measuring against the linchpin”:
“All male captives were forced to walk beside a wagon wheel. If their heads were higher than the linchpin (a pin inserted at the end of the axle) they were immediately executed... This technique was probably used to preempt against revenge attacks that were common between tribes at this time. If one tribe were to attack another, there was always the possibility that there would be a revenge attack soon after. By eliminating the older males, there was less chance of a counterattack from tribes that were in perpetual conflict due to centuries of distrust and robbery.”