The Bible makes numerous references to hell, everlasting fire. I will quote from the Douay-Rheims Bible.
Let's start with the Old Testament:
Which of you can dwell with devouring fire? which of you shall dwell with everlasting burnings? (Isaiah 33:14)
And they shall go out, and see the carcasses of the men that have transgressed against me: their worm shall not die, and their fire shall not be quenched: and they shall be a loathsome sight to all flesh. (Isaiah 66:24)
Judith is a deuterocanonical book. Its canonical status is disputed but we were given no definition of "Bible." Either way, it certainly doesn't help pro's case:
For he will give fire, and worms into their flesh, that they may burn, and may feel for ever. (16:17)
Now let's get to New Testament verses:
Whose fan is in his hand, and he will thoroughly cleanse his floor and gather his wheat into the barn; but the chaff he will burn with unquenchable fire. (Matthew 3:12 & Luke 3:17)
Depart from me, you cursed, into everlasting fire which was prepared for the devil and his angels... And these shall go into everlasting punishment: but the just, into life everlasting. (Matthew 25:41, 46)
Where their worm dieth not, and the fire is not extinguished. (Mark 9:47)
In a flame of fire, giving vengeance to them who know not God, and who obey not the gospel of our Lord Jesus Christ. Who shall suffer eternal punishment in destruction, from the face of the Lord, and from the glory of his power (2 Thessalonians 1:8-9)
As Sodom and Gomorrha, and the neighbouring cities, in like manner, having given themselves to fornication, and going after other flesh, were made an example, suffering the punishment of eternal fire. (Jude 7)
And the smoke of their torments shall ascend up for ever and ever: neither have they rest day nor night, (Revelation 14:11)
And there came down fire from God out of heaven, and devoured them; and the devil, who seduced them, was cast into the pool of fire and brimstone, where both the beast and the false prophet shall be tormented day and night for ever and ever. (Revelation 20:9-10)
Pro uses the exact words fallacy by saying that there's no verse in the Bible that says the damned are tortured with "greatest pain in Hell." Pro only tried to show that the "greatest pain" part wasn't in the Bible and not the "forever" part. Pro only did half of what the debate was about. That being said, trying to disprove one does disprove the entire claim, but it would make more sense to attack both points to make the case as sturdy as possible.
In Matthew 25:41, God tells the damned to depart from Him, showing that hell is separation from God. God is love and peace, so separation from God would be the greatest pain ever.
Also, the greatest pain could be the everlasting part. If you know the pain will never end, it will feel greatest. There is no escaping it. You won't be able to say it doesn't feel that bad.