Why do my students love the Joker so much? The guy has absolutely no redeeming qualities. He is completely mad, is an agent of chaos, loves to torture the innocent, has brought Gotham City to its knees on countless occasions, yet all the kids seem to love him. It is because he has what the Greeks called "hubris" or a flaw that makes him fallible even though he causes massive headaches for the protagonist (namely Batman). The flaw is that Batman is never beaten by The Joker even if The Joker has done something incredibly horrible. Batman always calmly defeats him.
In my first novel The Transgression Box , the villain was a metal box about 6 inches square with concave sides that caused the edges of it to be very sharp. It was an inanimate object, but it represented sin in the novel much like the One Ring does in Tolkien's epic trilogy. It could speak, but only to the mind of it's bearer, namely my protagonist Dornin. Creating such an unusual antagonist was a chore in that I had to give it a flaw that was not easily visible. It took much effort and planning, but the antagonist's flaw was my eureka moment in writing that book and I'd rather not spoil it for you if you haven't read it.
Here are a few tips to creating a villain for your novel that readers will love to hate.
1. Planning - Plan your villain as if they were the main character of the novel and then give them even more details. Even if the reader never knows all the details about the villain and how they became so powerfully evil, you must know them back and front and inside and out. We still don't know much about Sauron, other than he was really bad and made the One Ring, but if you read Tolkien's appendix at the end of Return of the King and other notes he made, you will see that he planned that character out much more than Frodo or Bilbo combined.
2. Like/Hateability - The best villains have some quirk about their personality that makes them fun to hate or maybe there is a part of their personality that makes you laugh and cringe at the same time. Carnegie from The Book of Eli is a power hungry monster, but there is something about him that makes us like him. Possibly it is because in the post-apocalyptic wasteland he has constructed a town and has made some kind of civilization which then gives us secret hope. We still hate him because he is so cruel, but he does still retain some of his humanity even if it is barely noticeable.
3. The Puppet Master - One thing that is fun to do that I did in The Transgression Box was to use the main antagonist as a maguffin throughout the entire novel and at the end reveal an even greater villain waiting in the wings, pulling the strings of all the disasters that happen to your protagonist. I know this is a somewhat overused device, but it works well, and readers like to think they know everything until you pull out the surprise baddie and they get goosebumps. If you do this, you had better make sure the puppet master's construction is very deep. What made Emperor Palpatine from Star Wars so mysterious in the original trilogy was that he was this nefarious character we see briefly, and then when we see him in Episode VI we really hate him, but love how he has been pulling the strings the entire time.
4. Avoid Deus Ex Machina - When a villain places the hero in a terrible situation, don't bring some godlike character in to save them at the last moment. Part of what makes a good villain is that they are there to block the protagonist from reaching their goal. Good villains do a fantastic job of this, but the hero needs to be the one who foils the villain's well laid plans. When this happens, it will endear your reader to your hero even more.
5. Don't Be Afraid to Get Nasty - A majority of the fiction I have read where the villain is weak or pointless is one created by a writer who is afraid to write about something really bad or scary. Even if you are writing a children's book you should make your villains (if you use them) really bad. Take a look at this list of scary children's book villains for examples of the ones that still give us the creeps. Bob Kane's original vision of The Joker was what was represented by Heath Ledger's performance in The Dark Knight. However, during the "comics code" of the late '50s, he was forced to tame the character down so that the Ceasar Romero version of the character was the norm. He had to effectively hamstring a great villain. Today, Joker is back to his full evil glory and is now the top rated villain of all time.
6. The Word of the Day is "Hubris" - Create a fatal flaw in your villain that is not readily visible to your hero but is discovered later in the novel. You have to consider that the flaw must be something that humanizes the villain or makes them back off or ultimately leads to their destruction. However, killing off your villain may be problematic if you want to use them in further novels. The Joker has died in the comics countless times, but then (oops!) he really didn't "die". It only looked like he did. I think he regenerates.
I am inspired to create villains from nightmares, daydreams, bad people from history and other sources. The point is that your hero is only as good as the villain they face.