Our 8th grade RC teacher Miss Seacord told us we must never assume even Hitler went to hell. I thought that is the sin of presumption, assuming to know God's will. But more recently someone told me that's actually the sin against Hope. And no Christian is allowed to do it.
Sins against hope include presumption, as well as despair. Both involve "assuming to know God's will". But when you bring up Hitler, that adds another element: Justice, which demands that un-repented wrongdoing be punished. If anybody goes to Hell, I hope it's Hitler. A meticulous theologian might say it's okay to think Hitler went to Hell, if that was God's will, but we can't assume that, 'cuz Der Fuehrer might have repented the minute before he died. But it would be wrong to delight in that. That would be a sin, not against hope, but against charity ('cuz we must love all of our neighbors, even monsters like Hitler.) Some of the early church fathers were less meticulous: --They shall be tormented with fire and brimstone in the presence of the holy angels, and in the presence of the Lamb: And the smoke of their torment shall ascend up forever and ever. Rejoice over her, thou heaven, and ye holy apostles and prophets; for God hath avenged you on her. Revelation 14:9-11; 18:20, 19:3. --Which sight gives me joy??As I see illustrious monarchs groaning in the lowest darkness, Philosophers as fire consumes them! Poets trembling before the judgment-seat of Christ! I shall hear the tragedians, louder-voiced in their own calamity; view play-actors in the dissolving flame; behold wrestlers, not in their gymnasia, but tossing in the fiery billows. What inquisitor or priest in his munificence will bestow on you the favor of seeing and exulting in such things as these? Yet even now we in a measure have them by faith in the picturings of imagination. Tertulian (early Christian theologian, De Spectaculis, Chapter XXX. (he later embraced the Montanist heresy, so who knows where he ended up.) --In order that the happiness of the saints may be more delightful to them and that they may render more copious thanks to God for it, they are allowed to see perfectly the sufferings of the damned. So that they may be urged the more to praise God. The saints in heaven know distinctly all that happens to the damned. Saint Thomas Aquinas, Summa Theologica, Third Part, Supplement, Question XCIV, "Of the Relations of the Saints Towards the Damned," First Article, "Whether the Blessed in Heaven Will See the Sufferings of the Damned?")