The relationship between a person and their parents forms the very foundation of gratitude and moral development. When an individual repays this ultimate good with evil, despising the ones who granted them life, they undermine their own existence and bring about absolute physical and spiritual ruin.
This act of hostility displays extreme ingratitude toward those who partnered with God in creating the child and endured great hardship for their sake [עמנואל הרומי]. Such behavior blocks a person from accepting moral guidance. It destroys their capacity to show gratitude to anyone else, eventually leading them to deny God, the ultimate Creator, which in turn tears apart the entire social order [רלב״ג]. The motivation behind such a dark act varies. It may stem from deep pessimism, where a person views life only as suffering and blames their parents for bringing them into the world. Alternatively, it can be driven by pure greed, as a child secretly wishes for their parents' death to quickly inherit their wealth [מלבי״ם]. On a symbolic level, the father and mother represent intellect and the Torah; turning against them is akin to despising divine commandments and basic logic [עמנואל הרומי]. Furthermore, this moral collapse is often the final stage of a steady decline. A person who becomes accustomed to gossiping and betraying the trust of others will inevitably sink to the ultimate low of turning on their own parents and exposing their most private secrets [עמנואל הרומי].
The consequence for such profound betrayal operates on two complementary levels. In this world, a person's guiding light represents their success, fortune, and God's protective providence. As a punishment, this divine protection is completely removed. When sudden disaster strikes, plunging the person into a state of total darkness, they are left entirely without mercy, hope, or any light to guide them to safety [רש״י, מלבי״ם, עמנואל הרומי].
Yet, one might wonder why some individuals who treat their parents terribly seem to live long and comfortable lives. To address this, commentators look beyond the physical world, viewing the person's inner lamp as the human soul itself. The ultimate consequence unfolds on Judgment Day and in the afterlife, where the soul is entirely cut off from the source of life. This deep darkness represents a spiritual void or hell. In the physical world, a person who suffers can always choose to repent and reignite their spiritual light. However, the punishment in the world to come is absolute and final. Like a flame that suddenly detaches from its wick and dies out [מצודת ציון], the soul is extinguished in a place of total blackness and death [מצודת ציון, מלבי״ם, ביאור שטיינזלץ], leaving no possibility of return, fading away forever [אלשיך, אבן עזרא, מצודת דוד, עמנואל הרומי].