The Big Bad Evil Guy
The villain of your story is arguably the most important character-- even more important than the protagonist. A good villain will challenge your other characters. A great villain will drive your story. When characterizing your bad guy, not only do you have to define why they are the way they are, but you also have to make them reasonable. You can't just give your villain a tragic backstory and call it a day, because oftentimes that's not what makes a villain a villain. There has to be some deeper reason behind it. You have to design a character with such depth that your readers can understand them. You know you've done your job well when your readers begin to sympathize with them. Take Draco Malfoy for example. He bullies Harry Potter and all of his friends, and just generally isn't a good person. But for some reason, fans of the Harry Potter series love Draco, and some even prefer him over the other characters. That's becaus...