I love how the author is finding creative ways for Elma to win the battles while staying consistent with his powers and limitations. Yeah, he won only thanks to the psychological warfare.
Another important detail was that he purposely set up his scare tactic before showcasing his power: "Hey Guild Lady, is it okay if we end up killing the enemy?"
The bratty at first scoffed his question but when she saw his display of power, she quickly remembered that he was going for the kill and this conviced her to make a decision.