It was basically a pit the Dokkaebi dug for themselves. That's what they get by creating a disaster out of a previously good person. The disaster of questions obviously never was a good person to begin with, so there was no such risk with him. Shin Yooseung seems to be stupidly overpowered, so maybe the Dokkaebi got too greedy for their own good. Although that seems to be a highly recurring fault of theirs.
I'm telling you. Skin. The. Goat. Imp. This dude has found loopholes and workarounds for even the most basic and absurd of situations. Find one and put that tiny prick in a microwave like he deserves. Turn him into an intermediate hot pocket.
I'm not sure what the untranslated text says/implies, but at least with the translation text, 'defeat' and 'kill' are not the same thing. Hell, if you want to play with semantics, you could 'kill' the disaster if she gives up being the disaster.