Karma is the law of moral causation. 'What goes around, comes around'
'Do unto others as you would have them do unto you'
There are many people that think that KARMA is revenge. Someone has hurt you and this gives you the right to hurt them. No! Nobody has the right to hurt any living thing.
KARMA is: You go out of your way for another, and that action comes back to you; not necessarily by the person you helped, but somehow, some day someone does something for you. You get what you give, good or bad.
The consequences of someone else's actions are not your concern. Karma is NOT about revenge. The way you react to a situation is your Karma, if someone handles the same situation badly that is none of your business, it is their Karma.
Karma-Sanskrit: कर्म; means action, work or deed; it also refers to the principle of causality where intent and actions of an individual influence the future of that individual. Good intent and good deed contribute to good karma and future happiness, while bad intent and bad deed contribute to bad karma and future suffering.
Your Karma is about YOU and only YOU. What YOU do/say returns to YOU in kind. You are not responsible, nor can you control, anyone else's Karma. If YOU want to get more, give more. This refers to anything happiness, love, money, anything. YOU GIVE, YOU GET! That's how the universe works. So be good and do good.