One thing we often don’t like to think about when designing characters is their darker sides.
Today, write about the most rude thing one of your fictional characters–preferably your “hero” or heroine–has ever done. If you prefer to journal rather than write fiction, write about the most rude thing you feel you’ve ever done. Try not to soft-pedal this–in other words, don’t give in to the temptation to write about something that could be re-defined in a positive manner such as simply “being honest” or making a mistake. Go for honest-to-goodness, downright rudeness. Maybe your character was in a bad mood, maybe he displaced his anger from one thing onto another person, or perhaps he was totally unaware of the impression he was making (did he lack empathy? Was he simply distracted?).
Then write about your hero from the offended person’s point of view for a little while (or write the entire thing from that person’s point of view). Imagine how your character (or you, if you’re journaling) must have seemed in that moment. Does he seem like a totally different person? How does this change your view of your character?