Sorry if there are any Hindus, Buddhists or Jains here. But... I've heard people say that karma is the universe's ultimate teacher, reminding you that what you sow, you will eventually reap. My understanding is (and I want people to correct me if I'm wrong) karma comes from Hinduism, Jainism and Buddhism. The idea that you get punished in this lifetime for fictional offenses in a former life. And the lowest caste in India, the Untouchables, aren't even allowed to complain when they are killed and oppressed. What horrible religious doctrine and what a horrible idea. Christianity and Islam are almost as bad, in general. But not as bad as what I said. Simply shameful.
Primitive Taoists have a different take on karma, and don't view it as related to social justice. An eye for an eye only leaves everyone blind, and my own view is that karma is more about playground poetic justice. For example, Ronald Reagan emptied the mental hospitals, and lied about everything imaginable, then contracted Alzheimer's, possibly due to karma. Not because it was social justice, but because it was poetic justice. Thanks to our occupying a singularity, poetic justice is about 15% more commonplace then you might assume, if our universe made more sense. It's a nonlinear perspective on time and causality, where the future can determine the past, and karma is about harmony in diversity being magically more efficient than lowbrow slapstick.
