In its most simplistic version, karma law states that whatever we intentionally do will be rewarded in the future according to our original purpose: if we acted with good heart, we will have a good reward, whereas something bad will happen to us to make up for our ill thoughts. Future is a wide concept for budhists because not only involves our present life but all our future reincarnations - definitely too far ahead to be considered by many people. If I had my way I would make the reward instantaneous. That would create a conditioned reflex in evil people and after some time they will bear in mind that bad actions should be avoided and good actions encouraged.
For example, as soon as my landlady ("landwhore" would be more appropiate) told me that she will increase my rent up 5%, she should have developed a venereal disease. Then she would associate increasing rent over the legal 3.2% with disgrace. From then on she would think twice about raising rents more than what is stipulated by law. Not that she is the sharpest tool in the shed, but if dogs can learn something by reflex conditioning, she - being a bitch - can.
Last year my boss told me that my rise will be 0.3% over the mean, in order to diminish the differences between the lower salaries and the higher ones. He should have had a heart attack right after that, and stay some time at the hospital. That 0.3% is worth roughly 70$ gross per year. With that he was trying to deceive me into thinking that I was somewhere closer the higher salaries. But that heart attack would have come handy because the next time he would try to actually make a difference and be fair.
I know that thinking this is actually sick and that if my wishes of instant reward came true, I would be now suffering an electric discharge from the keyboard. I deserve it, but so do they and at least I know that I am doing wrong; they are just selfish bastards who ignore that they are going to spend eternity burning in hell or be reincarnated as cockroaches in future lifes. Until they become aware of that fact (I must believe that it is a fact, that some sort of justice exists) they will be spreading evil among those less fortunate than them.