Comment by Jujutsu kaisen on Bad Friend - Season.2 Chapter 44

@Jujutsu kaisen Simply put: Rigon's mother was part of the Magyo cult and they basically use dark magic. Because she wanted to hide where she is from, she sought out a husband who doesn't have influence and won't question anything. Husband has an inferiority complex and is jealous of his wife and thinks he is undeserving, still wants another chance. He then finds out, that his wife is part of the cult, which makes him despise her, so he kills everyone with poison, including his wife, excluding his son.