Char's getting better with her spellwork. Good to have friends, Haruto could probably handle this, but an entire army dying likely means it would be a permanent problem - and that would be more work.
There are only 2 cases of Haruto killing. First is the "bandits" that hurts his father('s army); second is the mages that summoned the monsters(doesn't look like he kill them in the manga, but in the novel he intended to pardon them until he learnt that Char was the target).
He also was on the edge of killing the Queen the whole time for giving the order to target char, if not for his father's advice. Also that one unlucky demon that we haven't seen in the demon's retirement house.
I can understand getting stopped by magic and magical girls, but how the heck did these sorry-ass soldiers get driven back by skeletons throwing their skulls? You have spears! Bat the projectiles away!
That little shit and the emperor are DEFINITELY getting a visit from Haruto after this like the way he visited the queen. Haruto gets another demon to add to his collection and the emperor will be under his control, I’m calling it. Pleaseeeee