We see the vengeance motif in many movies. It captures us. It goes like this.
Person B hurts Person A. Either directly, or, often, indirectly (hurts one of their loved ones).
Person A is going to "get even." To pay them back. To hurt them, we find ourselves hoping, far worse than what was done to them. This appeals to an ancient desire, beyond which humanity has not progressed.
We see the vengeance motif in Genesis 4, in a man named Lamech. We read,
Lamech married two women, one named Adah and the other Zillah. Adah gave birth to Jabal; he was the father of those who live in tents and raise livestock. His brother’s name was Jubal; he was the father of all who play stringed instruments and pipes. Zillah also had a son, Tubal-Cain, who forged all kinds of tools out of bronze and iron. Tubal-Cain’s sister was Naamah.
Lamech said to his wives, “Adah and Zillah, listen to me; wives of Lamech, hear my words. I have killed a man for wounding me, a young man for injuring me.
If Cain is avenged seven times, then Lamech seventy-seven times.”
We don't know who Lamech killed. We do know that, if someone tries to get back at Lamech, he will make them pay 77 times worse than what he did to the young man who hurt him. (Think here of Clint Eastwood, in the movie "Unforgiven.")
Centuries later, in these postmodern times, the vengeance motif still captivates human hearts. And often, it gets enacted on. Jesus came to reverse this. We see it in Matthew 18:21-22.
Then Peter came to Jesus and asked,
“Lord, how many times shall I forgive my brother or sister who sins against me?
Up to seven times?”
Jesus answered, “I tell you, not seven times, but seventy-seven times.
Craig Keener comments on this, saying: "Some scholars argue that Jesus here reverses the principle of vengeance in Genesis 4:24 (77 times). Hyperbole reinforces the point." (Cultural Backgrounds Study Bible, Kindle Locations 220322-220324)
Jesus reverses the vengeance motif. He overthrows the human desire to get even. He heals the bleeding wound that want to strike back.
Jesus shows us, not only by these words, but by his life, that forgiveness is more powerful than vengeance.