Heaven, increases all feelings to their extreme quality. Hell, decreases all feelings to their minimum quality. So if someone dies feeling sorrow, rage, hate and goes to heaven they’re going to feel all those to their extreme, that is why god creating hell is actually an act of love because he wants us to feel sorrow, hate, rage as little as possible and feel love to its extreme.
The threat of punishments stop people from doing things. God told Adam and Eve that if they ate that fruit, they will surely die. They did it anyway. Hell exists to discourage us from sinning, yet allowing us free will, still. But we still chose to sin. So we’re damned.