Mercy is higher than justice, trumps justice, is better than justice and is the fulness of justice. This is clearly stated in Scripture and the Catechism.
St. Thomas taught this very clearly.
**Question 21. The justice and mercy of God
Article 3. Whether mercy can be attributed to God?
God acts mercifully, not indeed by going against His justice, but by doing something more than justice; thus a man who pays another two hundred pieces of money, though owing him only one hundred, does nothing against justice, but acts liberally or mercifully. The case is the same with one who pardons an offence committed against him, for in remitting it he may be said to bestow a gift. Hence the Apostle calls remission a forgiving: “Forgive one another, as Christ has forgiven you” (Ephesians 4:32). Hence it is clear that mercy does not destroy justice, but in a sense is the fulness thereof. And thus it is said: “Mercy exalteth itself above judgment” (James 2:13). **