Can you give me an example of karma? I've never seen it in action..?

Every time I get the most horrible things done to me, everytime time I see people being wronged, they're told "Don't worry, karma will give the wrong doer what they deserve, and you will be rewarded" To me it's starting to seem like the whole "Stop complaining cause you're poor, God will reward you in the afterlife" thing that was used to keep peasants down by the government. I mean, when will I be rewarded? from experience, people who are wronged I.e bullied, are more likely to become bullies, and have a sh*t life than grow up to be a millionaire...