AgnosticBoy wrote: the concept of eternal punishment is still mentioned in the Bible in my opinion.
I could only find one reference to eternal punishment in the Bible (KJV). And the context of it applies to those who do not take care of the hungry, thirsty, strangers, naked, sick, and prisoners.
[Mat 25:44-46 KJV] 44 Then shall they also answer him, saying, Lord, when saw we thee an hungred, or athirst, or a stranger, or naked, or sick, or in prison, and did not minister unto thee? 45 Then shall he answer them, saying, Verily I say unto you, Inasmuch as ye did [it] not to one of the least of these, ye did [it] not to me. 46 And these shall go away into everlasting punishment: but the righteous into life eternal.
I expanded the search to verses on torment and found two passages.
Those who worship the beast will be tormented. Though it's not clear it would be eternal, only the smoke is said to rise for ever.
[Rev 14:9-11 KJV] 9 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, 10 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: 11 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.
Rich man was in torment in hell (Hades), though it's not clear this is eternal either.
[Luk 16:23 KJV] 23 And in hell he lift up his eyes, being in torments, and seeth Abraham afar off, and Lazarus in his bosom.
If we expand it further to eternal fire, those who give over to fornication (ekporneu�) and after strange flesh will suffer eternal fire. But, it's not clear this is some kind of eternal torment, but destruction.
[Jde 1:7 KJV] 7 Even as Sodom and Gomorrha, and the cities about them in like manner, giving themselves over to fornication, and going after strange flesh, are set forth for an example, suffering the vengeance of eternal fire.