Vengeance is His. Not ours. Perhaps I'm just making a semantical difference in English that's not there in the Greek, but why does it say that He'll re-pay instead of just saying that He'll pay? All of the vengeance and all of the payments are filtered through Jesus Christ at the Cross so that what reaches us is naturopathic and related to the homeostasis of the whole Creation rather than being just a personal bone to pick with each of us of how sinful we've been or whatever. Although in quoting this, it does say in Hebrews 10 that it's a fearful thing to fall into the Hands of the living God, is it not a more fearful thing to not fall into the Hands of the living God? And is it not an even more frightful thing still to fall into the hands of men? (2Samuel 24:10-14) All vengeance was His at the Cross.
A careful re-reading of 2Thessalonians 1 will show that the affliction and retribution that is coming upon those who don't obey the Gospel isn't because of their relationship to the Gospel, per se, but it's related to how they've been treating those who are baring the Gospel to all of mankind, and the eonian destruction is while they're away from the Presence of the Lord and the glory of His Power. Romans 1 says that the Gospel is the Power of God. If you would entertain the thought of the Gospel exclusively being His power -- the extent and totality of it -- just for the purpose of meditating on the New Testament a little more closely along the lines of references of power, the Gospel, and these judgments, then you could gain a deeper insight into it that wouldn't otherwise by afforded by your other thoughts. And as you pleased, you could always return to your own thoughts afterwards. Just for an illustration and a meditation though, take that literally and see how far that takes you into the New Testament as far as insight.
Wrath only exists where the Cross isn't known. And it only leads to the Cross which is the embodiment and consummation of the wrath of God. And after entering into the light of His Cross and Blood, there is no more offering for sin. Therefore, there is no more payment for sin. The wages of sin is death, but St. Paul called it a righteous judgment/assessment in 2Corinthians 5 that when One died for all, therefore all died so that those that are coming to life through the Gospel would no longer live for themselves but for Him Who died for them and rose again from the dead. All vengeance points to the Cross. All vengeance leads to the Cross. All vengeance is dispensed at the Cross, not towards humanity or the Creation but towards Jesus Christ. And He's the One "re-paying" because all payments are filtered through Him. His Cross is the place where all payments due have been paid. And there are no outstanding balances yet to be paid. Our Lord simply says in 2Corinthians 5 "Just go and get 'em. Bring 'em all to Me!" All that's left is the restoration and discipleship of every life to God through the Gospel. All that's left is the public declaration to everyone that they're free of all of this sin, and if they'll let Him, then Jesus Christ will wipe their consciences clean. The "New Birth" is the new birth of the conscience. It's God's stamp that all is free and clear; holy, blameless, above and beyond reproach. His only request is that we continue in this Gospel; this Covenant that He's made with all of Creation and that according to the liberty granted through this Gospel that we would each begin to love one another fervently from that pure conscience.