Scattered throughout the Old Testament, there is a concept of God being jealous and vengeful. Christ corrected such concepts.

The Old Testament was written by a variety of authors, with a varying degree of moral understanding, and then altered by "the lying pen of the Scribes;" so it has falsehoods scattered throughout it.

A false concept of vengeance has its origins in Exodus 20:5, where Moses, presenting the Ten Commandments, supposedly says of God:

For I, the Lord your God, am a jealous God, inflicting punishment for their fathers' wickedness on the children of those who hate me, down to the third and fourth generation; but bestowing mercy down to the thousandth generation , on the children of those who love me and keep my commandments.

Christ taught non-vengeance, non-retaliation and love of enemies for both God and humans (Mat 5:38:48):

...for his sun rises on the bad and the good, he rains on the just and the unjust.

A transitional concept was expressed by Jeremiah (31:28-30):

As I once watched over them to uproot and pull down, to destroy, to ruin, and to harm, so I will watch over them to build and to plant, says the lord. In those days they shall no longer say, 'the fathers ate unripe grapes and the children's teeth are set on edge,' but through his own fault only shall anyone die: the teeth of him who eats the unripe grapes shall be set on edge.

There was a battle in writing the Old Testament between the moral world and fakes and frauds. But moral prophets like Jeremiah couldn't say other writers were liars and fakes; so he said God will operate by a new standard in the future.

It's not easy to correct the concept of vengeance, as demonstrated by capital punishment, which has no purpose but vengeance.

The attack upon sin is not the same as vengeance. Vengeance extends beyond the problem and adds to it. Ending sin reduces problems. To not end sin is to be partially responsible for it.