Andrew Louth in “Introducing Eastern Orthodox Theology” writes the following about “Universal Salvation” in his last chapter of the book, The last things and eternal life:

“There is a deeper reason for Origen’s conviction of final restoration for all: for him it is inconceivable that Christ is to remain in sorrow for all eternity (after commenting on how Christ weeps over his sins as he wept over Jerusalem), on account of the failure of any rational creature to respond to his love and benefit from his sacrifice.

Whereas in Western theology, such a conviction rapidly dies out, in Orthodox theology hope in universal salvation, based on a conviction of the boundlessness of God’s love, has never gone away. St Gregory of Nyssa interprets the words of the apostle Paul’s teaching that God will be ‘all in all’ (1 Cor. 15.28) to mean the ‘complete annihilation of evil.’ St Maximos the Confessor likewise holds out the hope of the salvation of all. The grounds for this are principally the long-suffering love of God for all creation, and also the conviction that evil is without substance, but is rather a corruption of distortion of what is good. These two motives find striking expression in St Maximos’ contemporary, St Isaac the Syrian, who asserts that,

‘there exists within the Creator a single love and compassion which is spread out over all creation, a love which is without alteration, timeless and everlasting… No part belonging to any single one of all rational beings will be lost, as far as God is concerned, in the preparation of that supernatural kingdom’

and then adds, quoting Diodore of Tarsus, ‘not even the immense wickedness of the demons can overcome the measure of God’s goodness.’ The pain of hell is the result of love: ‘those who are punished in Gehenna are scourged by the scourge of love… The sorrow caused in the heart by sin against love is more poignant than any torment,’ Evil and hell cannot be eternal: “Sin, Gehenna, and death do not exist at all with God, for they are effects, not substances. Sin is the fruit of free will.  There was a time when sin did not exist, and there will be a time when it will not exist.’

The Orthodox hope, amounting to a conviction among many theologians, is that there is nothing beyond the infinite love of God, that there is no limit to our hope in the power of his love, at least regards as a legitimate hope the universal salvation of all rational creatures, maybe even of the devil and his demons.”

‘God will punish all atheists. They will burn in hell in everlasting fire’.
Obviously upset, the Staretz said,
‘Tell me, supposing you went to paradise, and there looked down and saw somebody burning in hell-fire – would you feel happy?”
‘It can’t be helped. It would be their own fault’, said the hermit.
The Staretz answered with a sorrowful countenance:
‘Love could not bear that, he said, “We must pray for all.”

– Saint Silouan of Athose (one of the greatest Orthodox saints in recent times)