Reply Obj. 1: He who takes vengeance on the wicked in keeping with his rank and position does not usurp what belongs to God but makes use of the power granted him by God. For it is written (Rom. 13:4) of the earthly prince that "he is God's minister, an avenger to execute wrath upon him that doeth evil." If, however, a man takes vengeance outside the order of divine appointment, he usurps what is God's and therefore sins.
Reply Obj. 2: The good bear with the wicked by enduring patiently, and in due manner, the wrongs they themselves receive from them: but they do not bear with them as to endure the wrongs they inflict on God and their neighbor. For Chrysostom [*Cf. Opus Imperfectum, Hom. v in Matth., falsely ascribed to St. Chrysostom] says: "It is praiseworthy to be patient under our own wrongs, but to overlook God's wrongs is most wicked."
Reply Obj. 3: The law of the Gospel is the law of love, and therefore those who do good out of love, and who alone properly belong to the Gospel, ought not to be terrorized by means of punishment, but only those who are not moved by love to do good, and who, though they belong to the Church outwardly, do not belong to it in merit.
Reply Obj. 4: Sometimes a wrong done to a person reflects on God and the Church: and then it is the duty of that person to avenge the wrong. For example, Elias made fire descend on those who were come to seize him (4 Kings 1); likewise Eliseus cursed the boys that mocked him (4 Kings 2); and Pope Sylverius excommunicated those who sent him into exile (XXIII, Q. iv, Cap. Guilisarius). But in so far as the wrong inflicted on a man affects his person, he should bear it patiently if this be expedient. For these precepts of patience are to be understood as referring to preparedness of the mind, as Augustine states (De Serm. Dom. in Monte i).
Reply Obj. 5: When the whole multitude sins, vengeance must be taken on them, either in respect of the whole multitude—thus the Egyptians were drowned in the Red Sea while they were pursuing the children of Israel (Ex. 14), and the people of Sodom were entirely destroyed (Gen. 19)—or as regards part of the multitude, as may be seen in the punishment of those who worshipped the calf.
Sometimes, however, if there is hope of many making amends, the severity of vengeance should be brought to bear on a few of the principals, whose punishment fills the rest with fear; thus the Lord (Num. 25) commanded the princes of the people to be hanged for the sin of the multitude.
On the other hand, if it is not the whole but only a part of the multitude that has sinned, then if the guilty can be separated from the innocent, vengeance should be wrought on them: provided, however, that this can be done without scandal to others; else the multitude should be spared and severity foregone. The same applies to the sovereign, whom the multitude follow. For his sin should be borne with, if it cannot be punished without scandal to the multitude: unless indeed his sin were such, that it would do more harm to the multitude, either spiritually or temporally, than would the scandal that was feared to arise from his punishment. _______________________
SECOND ARTICLE [II-II, Q. 108, Art. 2]
Whether Vengeance Is a Special Virtue?
Objection 1: It seems that vengeance is not a special and distinct virtue. For just as the good are rewarded for their good deeds, so are the wicked punished for their evil deeds. Now the rewarding of the good does not belong to a special virtue, but is an act of commutative justice. Therefore in the same way vengeance should not be accounted a special virtue.