JWs and SDAs do not believe that hell is an eternal place of suffering. They use this verse to teach that the soul of a sinful man dies, which means he is annihilated.
Ezek 18:20 The soul who sins is the one who will die. A son will bear no guilt because of the error of his father, and a father will bear no guilt because of the error of his son. The righteousness of the righteous one will be accounted to him alone, and the wickedness of the wicked one will be accounted to him alone.
This death refers to the second death.
Rev 21:8 But as for the cowards and those without faith and those who are disgusting in their filth and murderers and the sexually immoral and those practicing spiritism and idolaters and all the liars, their portion will be in the lake that burns with fire and sulfur. This means the second death.”
The lake of fire is an eternal place of torment.
Rev 20:10 And the Devil who was misleading them was hurled into the lake of fire and sulfur, where both the wild beast and the false prophet already were; and they will be tormented day and night forever and ever…14 And death and the Grave were hurled into the lake of fire. This means the second death, the lake of fire.
These verses prove that hell is eternal.
2 Thessalonians 1:8-9 in a flaming fire, as he brings vengeance on those who do not know God and those who do not obey the good news about our Lord Jesus. These very ones will undergo the judicial punishment of everlasting destruction from before the Lord and from the glory of his strength,
Matthew 26:24 True, the Son of man is going away, just as it is written about him, but woe to that man through whom the Son of man is betrayed! It would have been better for that man if he had not been born.”
If death throws that man into non-existence, it would be no different if he had not been born.
Mark 9:47-48 And if your eye makes you stumble, throw it away. It is better for you to enter one-eyed into the Kingdom of God than to be thrown with two eyes into Ge·henʹna, where the maggot does not die and the fire is not put out.
Revelation 14:9-11 Another angel, a third, followed them, saying in a loud voice: “If anyone worships the wild beast and its image and receives a mark on his forehead or on his hand, he will also drink of the wine of the anger of God that is poured out undiluted into the cup of His wrath, and he will be tormented with fire and sulfur in the sight of the holy angels and in the sight of the Lamb. And the smoke of their torment ascends forever and ever, and day and night they have no rest, those who worship the wild beast and its image and whoever receives the mark of its name.