1. First, God's justice is a function of his love. This is important because the two are usually seen in tension with each other, with justice being the primary. So someone might in effect say, "God finds a way to be loving within the framework of his justice." I disagree. "Mercy triumphs judgment."
2. Many biblical models people latch on to here are "not fully cooked." For example, the high point of Scripture on collective judgment is Ezekiel 18--"The person who sins is the one who will die"... not the people or group of the one who sins. That is not to negate corporate consequences or corporate correction. It is to say, however, that OT thinking that sees an entire people as defiled and worthy of direct punishment because of the sins of a few is incomplete biblical thinking. Any biblical theology of judgment must start with Ezekiel 18 and Jesus as the center point, "clear" scriptures.
Which leads me to the function of judgment as I see it:
1. To redeem the individual so judged.
That is to say, justice and judgment from a Christian standpoint is often intended to form and redirect the individual so judged. It is not for punishment but for training and discipline (Hebrews 12).
2. To protect or redeem a broader group of which an individual is a part.
I thought here of the man in 1 Corinthians 5 who is removed from the Corinthian church for two reasons: to try to drive him to repentance (number 1 above) and to protect the church from his corrupting influence. That is this second function of judgment.
3. As a final act of removal, when a person is not redeemable, with the accompanying terror of complete removal from God's presence.
This is what we call hell.