The Deal: A Horrid Mistake

I've made many deals in my demon life, ones to grant wealth, ones to grant power, ones to grant love, ones even to grant health, and many more. I have never regretted a deal, until now at least. This deal, no this person, was different. He didn't make the deal for himself, he made the deal for others, and not something cheesy like they fall in love with their crush. No he went to specific people and made all of their sadness go away. I didn't understand it, why didn't he make the deal for himself?

Then, he made the wrong person happy. It led to death and destruction, which for a demon that was a fun thing. But not this, this was actually making heaven and hell crumble. But I didn't know that, then.