I was going to make a long comment, but I thought I might as well just give a "short" answer.
I must say firstly, that anyone that claims to have read the Bible and denies Hell's existence, is, at best, deceived, and at worst, insane.
The foundational belief of Christianity is that Jesus died for our punishment, so that we wouldn't have to.
Perhaps the person most clear about this is the man Himself:
Joh 3:16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
Jesus goes into some good detail on hell in several places in the Bible, and actually talks about it more than any other person in Scripture.
Mat 25:41 Then shall he say also unto them on the left hand, Depart from me, ye cursed, into everlasting fire, prepared for the devil and his angels:
Mat 25:46 And these shall go away into everlasting punishment: but the righteous into life eternal.
Rev 14:9 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,
Rev 14:10 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:
Rev 14:11 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.
Luk 16:22 And it came to pass, that the beggar died, and was carried by the angels into Abraham's bosom: the rich man also died, and was buried;
Luk 16:23 And in hell he lift up his eyes, being in torments, and seeth Abraham afar off, and Lazarus in his bosom.
Luk 16:24 And he cried and said, Father Abraham, have mercy on me, and send Lazarus, that he may dip the tip of his finger in water, and cool my tongue; for I am tormented in this flame.
Luk 16:25 But Abraham said, Son, remember that thou in thy lifetime receivedst thy good things, and likewise Lazarus evil things: but now he is comforted, and thou art tormented.
Mat 23:28 Even so ye also outwardly appear righteous unto men, but within ye are full of hypocrisy and iniquity.
Mat 23:29 Woe unto you, scribes and Pharisees, hypocrites! because ye build the tombs of the prophets, and garnish the sepulchres of the righteous,
Mat 23:30 And say, If we had been in the days of our fathers, we would not have been partakers with them in the blood of the prophets.
Mat 23:31 Wherefore ye be witnesses unto yourselves, that ye are the children of them which killed the prophets.
Mat 23:32 Fill ye up then the measure of your fathers.
Mat 23:33 Ye serpents, ye generation of vipers, how can ye escape the damnation of hell?
These are just some of many Scriptures on hell directly out of the mouth of the Lord Jesus Christ.
I would find it hard to construe these passages any other way than presented, especially considering who is speaking, and who is being spoken to: Jesus, a Jewish Rabbi, is speaking to other Jews, most of which at least had a basic understanding of the Old Testament, which is also very clear about hell.
Many times when Jesus taught He spoke in parables (Matthew 13:10-17), in order to make the truth available only to those who were willing to dig for it.
But most of the time when He spoke about hell, (and maybe all, but I haven't counted) were not parables.
They were very plaintext.
This means that He meant what He said very literally: no figure of speech, no analogy. He wasn't speaking in mysteries: he expected his hearers (and readers) to understand what He was talking about. Otherwise, He was lying.
But of course, the Bible says Jesus never sinned (Hebrews 4:15), which means He never lied. So that means, according to the text, everything Jesus said that was not a parable, is intended to be believed as is, or not to be believed at all.
Given this, it is an indisputable fact that the Bible clearly states, at least from the Scriptures I've given, that Hell:
- Is eternal
- Is punishment
- Is the punishment that Jesus died for us to avoid (if we believe in Him)
Hopefully, this should make undeniably clear the Bible's reality of Hell.
As an aside, Bill Wiese also has good teachings on Hell. He allegedly went there for 23 minutes, and describes in detail the things he saw and felt, and backs it up with Scripture and answers a lot of common questions about Hell to clear up confusion.
Whether you believe him or not is up to you, but if anything, it's a very interesting listen.