There are lots of aspects to creating characters, I've found. One of the most important for me is the name. Once I have the right name, the character comes to life. I've had the wrong name for some of them, and they lie lifeless on the page, two-dimensional, forced characters. If I listen close enough, the character will tell me his or her name. Of course, that's the way writers speak of our own subconsciousness. It's not magic, the characters aren't really speaking to us, but it sure seems like it!
The first few novels I wrote had problems. The main one, I think, was with my protagonists. I got so many comments from agents that they didn't "fall in love" with her. I didn't want them to fall in love, but I did want them to represent me. My character was getting in the way. She wasn't vivid enough. One day it finally came to me. I'd been told many times, but for some reason it didn't take. Fiction has to be bigger than real life. No one wants to read about ordinary people, ordinary day-to-day happenings. They want what they read to be more interesting than that. I thought I had quirky characters, but they weren't quirky enough.
Do you choose someone you don't like for the victim? I don't think this is the best idea. Yes, it's cathartic to kill off someone who's done you wrong, and I can highly recommend it, especially in a short story or a piece for yourself. But for a mystery novel, you want to reader to care about catching the killer. The reader wants to see justice done and if a bad person is dead, it's been done--end of story--no need for the rest of the book. Kill off someone nice and the reader will be with you, wanting you to catch the bad guy.
That's where to put the person you detest. Make him the killer. Everyone can see what a bad person he is, right? Although a cardboard cutout all around bad guy IS a boring villain. You're only basing your bad guy on the hated person. Dig a little deeper for a real character. If you can see things from his point of view, if you can let the reader in on why he did what he did, draw a little sympathy for him, you'll have a more rounded, interesting character.
I'd like to hear about how other people view their characters. Do you have sidekicks? I've never gotten too much into those. But I like to have some other family members around, and at least one love interest.