Bad Guys -- How to write them (A-Z blog)

In some of the 'how to write" books I have read there is usually some advice about what to keep in mind about your book's antagonist...so here are my thoughts based on fiction I have read and written.

1. Some people in fiction (and in real life) are just evil.

While it's nice to think that everyone has some redeeming qualities and if you just polish them up some, they will reveal their inner gem. Some times this is true...sometimes, no matter how much work you put in, they are still just the same ole rock (I feel as if I am giving some relationship advice as well here). To make your characters real -- sometimes bad guys are just rotten to the core.

2. Even rotten characters have goals and motivations.

Have you ever noticed bad guys are more than willing to tell all their secrets (usually giving the hero time to rescue or the good guys time to get away). They have goals, albeit evil ones. Without these, what reason would they have to get up in the morning and what would keep your story going?

3. Bad guys are necessary for plot momentum.

Once upon a time, there were nothing but good people who all did good things and no one was mean of vindictive. No one wanted revenge and everyone was nice to everyone else all of the time. The End.

What makes a hero know if he's a hero if there is no need to fight the bad guy? No need to put things right? How do you know this one's a "good" guy or girl if you have no basis of comparison (again, I feel I am talking about more than fictional people here).

Bare bones of it -- our stories need the bad guys, but make 'em believable and real. And it's okay if your readers can empathize with the bad guys, but they should be cheering the bad guys on to win. Just my thoughts.