Monster, Dwaeji-ui Wang Recommendations
While the plot of both anime may be different, both have a similar tone and deal with disturbing and taboo themes. Both anime have a lot of violence and murder, and focus on characters who have suffered a lot during their childhoods. Both anime have characters with nihilistic views on life, who, in order to survive the violence and torture in their childhood, decide to become "monsters". So, becoming evil (or monster) is a key element in both anime, which is what makes the two similar.