If you're going to torture a character, I want to enjoy it. I'm not a sadist, I'm referring to poetic justice. It's a pretty common literary technique, but it's also very tricky. Few authors get it right. The thing about poetic justice is this: a little goes a long way.
The House That Martin Built
You'll see poetic justice a lot in storytelling. It's always satisfying when the villainous character meets his just desserts. We always root for the Road Runner to get away, and snicker when the coyote has the anvil dropped on his head. But if you drop too many literary anvils in your books, you're not longer a storyteller. You're a person who likes to dole out suffering. And of course, I've got an example.