Coincidentally, I just posted something on this topic. (I write for an apologetics blog.) It's longish but I'll copy-paste here in case you're interested in my take.

It is often suggested that the Christian doctrine of Hell is morally unconscionable. Understanding this doctrine to be that the nonbeliever is sent to a physical location where for his non-belief he is burned for all eternity, the skeptic makes the point that this is incompatible with the moral perfection of God. The claim that God is all loving and the claim that God punishes his creatures eternally for finite offences seem at odds. In what follows it will be my concern to show that this objection is based on a crude caricature of Hell that is quite different from what the church actually teaches. And we shall see that when that doctrine is properly understood there are no indefeasible moral objections against it.

The Problem

How will a morally perfect and all powerful being deal with those who by the end of their life have become incorrigibly bad? Let us first understand “incorrigibly bad” to describe a person who has exercised his free will to do evil to such a degree that he has finally developed an evil character. His natural desire is to perform bad actions and in particular to hurt and dominate others. God has good reason to allow moral evil while people form their moral character in this world. But there is no good reason for God to allow people to continue hurting others forever. I will now briefly discuss two alternative views about the fate of the incorrigibly bad before defending, but carefully qualifying, the traditional teaching of the church. My conclusion will be that while we may reasonably hope that Hell is empty its possible existence must be affirmed in view of human freedom.

Universalism

Why does God not simply force upon such people a good moral character? Some hold that God does just this—including Origen, an influential Church Father, and several contemporary theologians. [1] This view, because it entails that all people go to Heaven, is called Universalism. But forcing a good moral character upon an evil person is forcing upon them a character which they have persistently and knowingly chosen not to have. And if God is to respect the free will of persons in choosing their own moral character he must finally respect the moral character they have chosen. To do otherwise would be to rescind the free will he had originally given: God would then be a sort of moral totalitarian who ensures that, in the end, whatever choices people make, they become the sort of people God wants them to be with no ultimate freedom to determine the sort of person they want to be.

I have argued elsewhere that incorrigibly bad people are a possible outcome of any world in which all people enjoy significant moral self-determination; and that naturally good people will be naturally happy in loving communion with a morally perfect being. By contrast: Allowing oneself to become a collection of evil desires whose fulfilment is eternally frustrated by an all powerful being would be a deeply unhappy state. The question arises: If God will not force a good moral character upon such people, what is he likely to do with them?

Annihilationism

Christian theology holds that all things are sustained in existence by God from one moment to the next. Each one of us therefore stands in the same relation to God as the piano sonata to the pianist: The moment God ceases to consciously and deliberately sustain us in existence is the moment we cease to exist. This doctrine helps to introduce a second view on the fate of the incorrigibly bad: Annihilationism. Annihilationism holds that at the end of the world God simply ceases to sustain the incorrigibly bad in existence; and the incorrigibly bad, as a result, simply cease to exist.

Proponents of this view suggest that Bible verses which speak of evildoers being thrown into a lake of fire in fact symbolise their annihilation. “If talk of fire is to be taken literally or even as an analogy for the destiny of the wicked,” writes Oxford Professor of Philosophy Richard Swinburne, “the consequence of putting the wicked in such a fire would be their speedy elimination.” We have just noted that having all one’s desires frustrated by an all powerful being would be an inherently miserable state. And so perhaps God would eliminate evil people—particularly if that is what they wanted. It is this fate, annihilationists insist, that Jesus warned us to avoid in many places in the New Testament, such as Matthew 10:28,

And fear not them which kill the body, but are not able to kill the soul: but rather fear him which is able to destroy both soul and body in hell.