Every single karma for you (and against you) gets paid back.
Both types are paid many fold.
Only question is how long one waits for it to happen.

There is a school of thought that if people abuse you verbally they take a small percentage of your karma.
If they think of you badly, a smaller percentage of ur karma is now theirs.
If enough people abuse verbally a large percentage of your karma is now gone.

Conversely if you abuse someone verbally or in writing, a small percentage of their karma is now yours.
If you gather enough people to verbally or otherwise abuse someone, then you take on a substantial portion of their karma. (So some say) They become lighter.

I never believed that this was true in the past.
However, Narsi Mehta used to say, if you sing his bhajans, people will beat you with slippers... (your karma will be taken on by others).. same happened to Jnaneshwar Maharaj and Tukaram... so maybe there is truth in this.

One question asked is what’s the impact of the parents karma on children? Effect of prayers on children’s karma?
Ans: Parents karma can produce terrific good/bad repercussions for children as per karmic theory.

I know of several families where parents took huge bribes/caused good people lot of pain.
Children’s lives eventually got so screwed up... call it what you want but fits with karmic theory.

Old story: make what you will of it.
One senior well known minister known for severe heavy corruption. His daughter was in mad love with someone... that person died on the next day of a deal which caused a few families great pain.
Daughter went off the rails for years..

Another decades old story:
Politician who lusted after another person’s good looking wife.
He caused their break up, the man went mad, became drunkard, crashed .. died.
Politician a decade later screwed up completely.. lost everything.