The question in my mind is how can any man ever pay back God for all his sins? And since Jesus doesn't speak in terms of termination of existence, the thought of retribution is rather a frightening one because we know what we deserve. I understand the argument that death is just nothingness, but there is tension in scripture (if you just go on the English KJV words, anyway) that accepts as a given that these wrongs must be repaid...in full. And if not in Christ, then the individual has to answer for each one. If one sin is deserving of death, then proper justice requires multiple deaths for multiple sins. Even if there is an eventual end, the prospect of justice at God's hands is at once unanswerable and terrifying :
Wherefore we labour, that, whether present or absent, we may be accepted of him.
For we must all appear before the judgment seat of Christ; that every one may receive the things done in his body, according to that he hath done, whether it be good or bad.
Knowing therefore the terror of the Lord, we persuade men; but we are made manifest unto God; and I trust also are made manifest in your consciences.
2 Corinthians 5:9-11
And the third angel followed them, saying with a loud voice, If any man worship the beast and his image, and receive his mark in his forehead, or in his hand,
The same shall drink of the wine of the wrath of God, which is poured out without mixture into the cup of his indignation; and he shall be tormented with fire and brimstone in the presence of the holy angels, and in the presence of the Lamb:
And the smoke of their torment ascendeth up for ever and ever: and they have no rest day nor night, who worship the beast and his image, and whosoever receiveth the mark of his name.
Revelation 14:9-11
This, to me, sounds nothing like mere end of existence.