John Chrysostom

For what he says is somewhat of this kind. If sin had so extensive effects, and the sin of one man too; how can grace, and that the grace of God, not the Father only, but also the Son, do otherwise than be the more abundant of the two? For the latter is far the more reasonable supposition. For that one man should be punished on account of another does not seem to be much in accordance with reason. But for one to be saved on account of another is at once more suitable and more reasonable. …

Homily on Romans X ↗

Theophylact of Ohrid

Christ, he says, brought benefit not merely to the same degree that Adam caused harm. If sin was so powerful that through the fall of one all his descendants were condemned, even though they themselves did not fall, then how much greater and more abundant will be the effect of the grace of God the Father upon many, and not only His, but also of His Son. And the gift of God cannot be equal to the condemnation through the one who sinned.

Commentary on Romans ↗

Thomas Aquinas

After discussing the entry of sin into this world, the Apostle treats of the history of grace, which abolishes sin. And concerning this he does two things. First, he shows how the grace of Christ removed sin, which entered the world through one man; second, how it removed sin, which superabounded with the coming of the law, at now the law entered in (Rom 5:20). …

Commentary on Romans ↗