Of course there are false and fallen Christians in Hell. Doing good works, and identifying as a Christian, and calling yourself a Christian in public, but not really believing in Jesus counts for nothing. Look at Judas.
Also, consider Simon the magician. He even believed and was baptized, but he was a false convert anyway. He believed in miracles and the power of God, but he didn't really believe in God, and to my knowledge never repented. Jesus also taught about dead faith. I don't want to get into a debate about Sola Fide, but giving mere intellectual assent to the truth of Jesus being the Son of God and His Resurrection, but not repenting of one's sins, or not accepting Jesus' sacrifice personally, or not doing any good works, or not resisting sin, or changing anything at all about oneself, is that true saving faith?
A lot of these Hell visions are mutually incompatible, meaning that they can't all be literally true, and thus at least some of the claimants are either lying, were hallucinating, or under demonic suggestion. Worse, some of their reports contradict orthodox doctrine, as well as the Bible and Church Fathers.
Personally, I had a "vision of Hell" many years ago, and I have no idea if it was genuine or not, and so I don't tell anyone about it, at least not without a disclaimer.