It was pretty decent writing that Richter didn't, after all, really want to kill the two girls. He wasted a whole lot of energy to simply pummel them around as long as there existed the possibility that Frieren could be contained. Only after that he actually went for the permanent solution. However, in the previous episode he indicated he would try to kill one of them immediately. So, that was just a bluff, meant to demoralise the girls and possibly encourage Frieren to be hasty and make a careless mistake in her own fight, in order to hurry to save the girls.

Quote Originally Posted by MFauli View Post
Assuming that the threat to the world was not a pushover. You're right, that's a strong assumption going by how easily Frieren defeated everyone so far.
Saying the demons are pushovers because Frieren could defeat them is like saying olympics silver and bronze medal winners are pushovers because the gold medal winner did beat them. Frieren might be the most powerful mortal in that world right at that moment. Serie isn't powerful because she's a hikikomori who never leaves her room. Her power is purely theoretical, whereas Frieren has used all of her wits to come up with ways to slay demons and she's actually doing it as well.