Most horror villains are portrayed as being serious and threatening, but Freddy Krueger is different. He is a sadistic and twisted individual, but he also has a dark sense of humor. This makes him more unpredictable and terrifying than other villains, who are often predictable and formulaic.
His backstory is absolutely terrifying, especially as he targets children specifically, and his presence in these films is also really interesting. Him traveling through dreams and killing these young people in their sleep, playing on their fears and personalities, is a truly scary and intense concept.