I was speaking to someone recently who had suggested that Hell was empty or at least close to empty. He said he couldn't reconcile a loving God with souls in Hell (except Hitler, who always seems to get a pass from the no Hell crowd.) I said that while I agreed it was difficult there is free will and the consequences of it and there sure are a lot of mentions of Hell in the Bible for an empty place. And the Church clearly teaches about a "state of definitive self-exclusion from communion with God and the blessed" which is called "hell."
The guy I was speaking with later mentioned that he'd been to Fatima. I said that one day my wife and I would love to take the children there and I asked him how he reconciles the vision of Hell shown to the children in 1917 by the Virgin Mary if he believes Hell is empty. He said he didn't.
That vision was revealed by Sister Lucia, who wrote:
“Our Lady showed us a great sea of fire which seemed to be under the earth. Plunged in this fire were demons and souls in human form, like transparent burning embers, all blackened or burnished bronze, floating about in the conflagration, now raised into the air by the flames that issued from within themselves together with great clouds of smoke, now falling back on every side like sparks in a huge fire, without weight or equilibrium, and amid shrieks and groans of pain and despair, which horrified us and made us tremble with fear. The demons could be distinguished by their terrifying and repellent likeness to frightful and unknown animals, all black and transparent.”
Sister Lucia added:
“We then looked up at Our Lady, who said to us so kindly and so sadly: ‘You have seen hell where the souls of poor sinners go. To save them, God wishes to establish in the world devotion to my Immaculate Heart. If what I say to you is done, many souls will be saved and there will be peace.”Many souls. Not all. (Note: she didn't mention just Hitler.)
Obviously, no Catholic must believe in the children's' vision at Fatima. But if you do, you should probably consider it in its totality.