The Christian heart seeks reconciliation, not vengeance. To love someone, even someone who by all earthly accounts you should hate, is to desire that reconciliation on a newly turned-over leaf. To relate to that person the way it should have happened in the first place, in love and fellowship, and mutual honor.
That is the best balm for a wounded heart. After all, God did that for us. We wounded Him and gave Him every reason to hate us, even to the point of crucifying His Son (even if you're not Jewish, the fact that the Romans enabled the Crucifixion means that Gentiles also crucified Him by their sins). I mean, imagine having a child that did nothing wrong and a mob suddenly just shows up and nails him to a cross while mocking and beating him. If anything was to make you jump into a helicopter and shoot some hellfire missiles, that would be it. But God did something even better than that: He turned the hearts of some of those who were in that mob, and started over with them on a new leaf. So instead of dumping fire and brimstone on them, He made them into His own children, and they repented of what they had done.
He had every right and reason to just pull up all the lava in the earth with such force that it would shower everywhere on earth, drop asteroids on the earth, and make the sun explode to wipe everything out. Being God the Creator, He had the right, and being the Father of a crucified Son He had the reason. But thankfully, He figured out a better way to deal with the situation: in love.
And yes, it defies absolutely every aspect of human reasoning. And rightfully so! For human reasoning, since we are made in the image of God, is that justice must be served. But thankfully, the Crucifixion is the justice being served. Justice has already been done in Christ. Therefore, if those people who hurt you came to repentance and confess that Jesus is Lord, then the justice that should have been done to them has been done in Christ. Their punishment has been meted out fully - against Christ. God's vengeance against that person is satisfied fully in Christ. Just like how His vengeance for your sins has already been satisfied in Christ. The blood of Christ is infinitely far more valuable than the blood of mere men and women. The infinity of Christ's sacrifice is sufficient for all believers, for all time.
So in a very poetic manner of speaking, the greatest way you can take vengeance on those people... is to turn them to Christ.