The books of the prophets deal with God judging His people. (Jeremiah, Hosea, Isaiah, Jonah, Habakkuk, etc)
Aside from the books of the prophets, there is actually a book in the Bible titled "Judges." Imagine that, a whole book in the Bible dedicated solely to the judges of Israel that God appointed to judge His wayward children.
The Bible tells us God is the same yesterday, today, and forever(Hebrew 13:8). So if God judged in the Old Testament, He will still judge today, tomorrow, and for however long afterwards He needs to. Part of God's character is to judge people, because He is a just God. Being just means He has to judge those who have sinned. He may judge them, and decide to grant them mercy or grace, but He has still judged.
An example in the New Testament where God judges sinners (if you are unwilling to accept examples from the Old Testament, like some Christians are), would be the story of Ananias and Sapphira in Acts 5:1-11.
1Now a man named Ananias, together with his wife Sapphira, also sold a piece of property. 2With his wife's full knowledge he kept back part of the money for himself, but brought the rest and put it at the apostles' feet. 3Then Peter said, "Ananias, how is it that Satan has so filled your heart that you have lied to the Holy Spirit and have kept for yourself some of the money you received for the land? 4Didn't it belong to you before it was sold? And after it was sold, wasn't the money at your disposal? What made you think of doing such a thing? You have not lied to men but to God." 5When Ananias heard this, he fell down and died. And great fear seized all who heard what had happened. 6Then the young men came forward, wrapped up his body, and carried him out and buried him. 7About three hours later his wife came in, not knowing what had happened. 8Peter asked her, "Tell me, is this the price you and Ananias got for the land?" "Yes," she said, "that is the price." 9Peter said to her, "How could you agree to test the Spirit of the Lord? Look! The feet of the men who buried your husband are at the door, and they will carry you out also." 10At that moment she fell down at his feet and died. Then the young men came in and, finding her dead, carried her out and buried her beside her husband. 11Great fear seized the whole church and all who heard about these events.
God judged their greediness, and killed them because of it. God judges.