'Vengeance is mine sayeth the Lord' is actually a very compassionate line. When we personally get involved punishing or meting out what we perceive as deserved retribution to individuals or groups of people, even in small ways - when we take it upon ourselves to be the judge and executor of our notion of 'justice', even if the receiver is undeniably 'wrong', we make trouble for ourselves by involving ourselves in that person's story or karma. We've all accepted the Universal Law that what goes around comes around, but this isn't limited to aggression or negativity we direct at good, innocent people. It bounces back from anyone we lay it on. So even if this person who we think we're legitimately punishing seems to totally deserve it we are still creating the causes for the same violence to return to us. This is why 'Vengeance is mine sayeth the Lord' is such an important and compassionate line because God, or The All That Is, has no karma. 'God' has no need to worry about things bouncing back - that entity doesn't exist on the human plane and is immune to the dangers of getting involved in someone else's drama.
I'm saying that the Universal Law is not putting itself in danger by delivering the lessons or negative consequences to folks who've 'done wrong'. Humans are.
Beware choosing to be the punisher or the righteous deliverer of justice. It's hazardous to humans, not Gods.
We'd all do well to resist.