The ending, despite this entire movie being a Mind Screw.
In a meta-sense: this film is a favorite of those people who are in hospices and/or are dying. After the initial horrific shock of the film, it's quite comforting to those getting ready to embrace their death.
Louis: Eckhart saw Hell too. He said the only thing that burns in Hell is the part of you that won't let go of life, your memories, your attachments. They burn them all away. But they're not punishing you, he said. They're freeing your soul. So, if you're frightened of dying and... you're holding on, you'll see devils tearing your life away. But if you've made your peace, then the devils are really angels, freeing you from the earth.