Training Mistakes
If Anakin didn’t kill the Younglings in Episode III, Yoda probably would have done the job for him through sheer incompetence. I mean seriously, who does give children lethal weapons? Force or no Force guiding them, kids would start play fighting with a lightsaber the second you gave it to them. Although I guess there are such things as Training Lightsabers, I’m just going to assume this happened before those were put into use.
AHHHAHAHHAHAHAHHA
Point of detail? The Scholastic prequels to Phantom Menace pointed out that the apprentices all use training-sabres. They deliver the occasional burn at worst but do not dismember.