I already have a couple examples of karma like how Duncan was too trusting and for that he ended up dead, and how Macbeth saw Banquo's head after he was murdered. Any more?
Macbeth suffers from karma because his actions come back on him. You could also argue that Macduff does, since he does not stop Macbeth. The witches also have bad karma, because their plans backfire.
Malcolm seems to have enjoyed good karma. As Duncan's son and heir, he behaved with courage and with loyalty to his father and to his country. Malcolm (and also Donalbain) loved his father. When Duncan was murdered, Malcolm flees, not because he does not care that his father is dead and will be buried, but because he is smart enough to strongly suspect that his own life is in danger. Both Malcolm and his brother speak of their tears for their father before fleeing. After leaving Scotland, Malcolm works hard to see that Macbeth is overthrown, that Scotland's people are saved from tyranny, and that he assumes the throne as was his father's wish. All of these are accomplished, which could be interpreted as Malcolm's good karma coming back to him.
You've basically got the right idea. Karma basically means that we are all in control of our own lives and what happens to us by how we behave or act in the present. So when people do bad things, then bad things come back to them. (what goes around comes around idea)
Macbeth is finally defeated because "he had it coming to him." Although that's vague and not as specific as your examples, that's the right idea. Lady Macbeth became so blindly ambitious, her guilt eventually caught up with her in her insomnia. The same thing happened to Macbeth. They both struggled to sleep at night. Macduff should never have left his family during such unstable times. He then lost them all. Hopefully these give you some other ideas.