So the karma is not the principle it's idea. In upcoming points you will get know how it is a universal priciple or truth or whatever.

1. Like if do bad , bad happens to you .. Oh okay so like to get kill you have to kill otherwise you don't die. To get a cancer you have do a same amount of pain to somebody that is equal to your cancer.
2. Like escobar he is sellingdrugs and think for second how much crimes had been done and how much sufferings thag drugs have been caused. But he get kill by one bullet in seconds he bare no pain equal to he put out.

• Like a baby that is just born out but have no parents so think what had he done wrong to get that painful life. So if you say it's because of old life etc. Than stop i will talk about it later in other.
• Well 8 years old girl got rapped in india. Why? An innocent 8 year old girl comes to temple and got rapped. So where is karma playing justice ?

Well this is not what i mean you have be accountable for your actions but all i am just saying is that bad happens to good and good to bad ones but nobody can tell why and how? So stop asking for answers that are not here or may be you already know and move on to do something good that gives you happiness.