I forgot most of the plot but I do remember one arch. The main character cosplays as a demon king and tells a NPC that he would grant her wish. The NPC is a woman who is abused by her husband. Many players have tried to pass the level but they never managed to. The woman lost her son and tries to kill herself and the mission is to keep her alive until the last day. The MC helps her take revenge on her husband (who in fact killed the boy) and kill him and her mother in law(who was very abusive). Then the NPC tries to pull and UNO reverse on the MC but, sike, the MC made a loop hole in their deal. The main character and the male lead then lead all the other players out into safety, making the old players who were stuck in that dungeon for ages, owe them a favor. I do remember one of the supporting characters. It was a woman (?) who was a chain smoker and they would often give the MC advice and past clues. I read this story a while ago and it's been quite a time. After this novel I have read many more with similar plots.
This sounds like the last arc in "Learning God in Hand, I have the World". In that arc, there are multiple instances(?) And one of them sounds exactly like this.