The reason this happens with regularity is that the impulse to seek revenge is faulty to begin with. It is poor judgment and a lack of wisdom in surrendering to the inner belief this will right the wrong, the perceived grievance that is so troubling. And because it is out of alignment to seek vengeance and cause harm simply because one has been harmed, if the intended act of vengeance is carried out, it will be a Pyrrhic victory because it cannot truly make the original victim feel whole again. They will still have their wound, they will still have their feeling of diminishment, and causing suffering to their perpetrator will not truly replace what was taken from them. They have only returned the crime, so now there are two victims and two perpetrators having a kind of dance together. This will not end things but may in fact perpetuate the dance so that it continues further, and may even resume in another lifetime when the two come back together and have another round of similar attacks and retribution to continue the struggle.
The only answer that makes sense is healing through a return of love to all involved. This can be difficult to see and even more difficult to carry out by a person blinded by hatred, and that is the problem with inner beliefs, they cannot be overridden readily and may in fact require healing through Belief Replacement via a divine intervention to end the cycle. But this is doable through prayer and the right healing requests to arrange it to happen, and that is a wiser course of action to prevent what could be a virtually unending saga of action-reaction carried on through centuries of time to support an ongoing vendetta that only worsens the participants who cannot see the folly they embrace.