Demon means for their own sense satisfaction, they are prepared to do anything wrong. Just like this Kaṁsa. Kaṁsa, the elder brother of Kṛṣṇa's mother, and as soon as he heard an omen from the sky that, "You rascal Kaṁsa, you are taking your brother and sis . . . brother-in-law and sister in your chariot to their home in their marriage ceremony, but you, rascal, do not know this sister's son will kill you." "Oh? My sister's son will kill me?" Immediately caught up sister: "Finish my sister."
Vasudeva saw, "What nonsense you are doing? You are such a big king. And your sister, younger sister, and she is married in this auspicious moment. Why you are killing?" "No, she is the cause of my death." Then, "Your sister is not the cause of your death. Her son. That's all right. But I promise, all the sons will be delivered to you." Because it is the husband's duty to give protection. So some way or other, he saved the situation.
So this is the demon. He did not consider that, "Here is my poor younger sister. She's just now married. In jubilation she's going at her husband's home. How auspicious ceremony." And he was personally driving the chariot. But as soon as he heard that, "Oh, there is danger from my sister," he did not care anything, no relationship, no ceremony, no auspicity, nothing. This is demon. Demon means for his self-interest he can do anything nons . . . nonsense. That is demon. And demigod means he'll consider thrice before doing anything.