I wanted to write and ask you what you teach the punishment for sin is for unrepentant sinners at the final Judgement.

"... and to give you who are troubled rest with us when the Lord Jesus is revealed from heaven with His mighty angels, in flaming fire taking vengeance on those who do not know God, and on those who do not obey the gospel of our Lord Jesus Christ. These shall be punished with everlasting destruction from the presence of the Lord and from the glory of His power, when He comes, in that Day, to be glorified in His saints and to be admired among all those who believe, because our testimony among you was believed" (II Thessalonians 1:7-10).

"I tell you, no; but unless you repent you will all likewise perish" (Luke 13:3, 5).

""Therefore I will judge you, O house of Israel, every one according to his ways," says the Lord GOD. "Repent, and turn from all your transgressions, so that iniquity will not be your ruin. Cast away from you all the transgressions which you have committed, and get yourselves a new heart and a new spirit. For why should you die, O house of Israel? For I have no pleasure in the death of one who dies," says the Lord GOD. "Therefore turn and live!"" (Ezekiel 18:30-32).

"For the wages of sin is death, but the gift of God is eternal life in Christ Jesus our Lord" (Romans 6:23).

"And these will go away into everlasting punishment, but the righteous into eternal life" (Matthew 25:46).

"And I saw the dead, small and great, standing before God, and books were opened. And another book was opened, which is the Book of Life. And the dead were judged according to their works, by the things which were written in the books. The sea gave up the dead who were in it, and Death and Hades delivered up the dead who were in them. And they were judged, each one according to his works. Then Death and Hades were cast into the lake of fire. This is the second death. And anyone not found written in the Book of Life was cast into the lake of fire" (Revelation 21:12-15).

See also:

Questions and Answers regarding Sin
Questions and Answers regarding Hell