It’s a weird question, but if I had to answer, that would be vanity, that is, thinking that you’re better than other people. That includes being nicer and more caring than other people, as well as being better than those who think they’re better than you, because they think that and you don’t. Ultimately that includes considering yourself being somehow more evolved than animals, too.

Every ego is fundamentally narcissistic in nature, and ego of nice and caring people, too. Good people are secretly proud of their goodness and think they are better than bad people. True, authentic kindness doesn’t mind how it’s being treated, it makes no difference. Every time a person evokes a negative emotional reaction in you with their words, you secretly think that you are better than them.

The extreme of this “I’m better than everybody else” syndrome is basically NPD, Narcissistic Personality Disorder. That would be the polar opposite of spiritual enlightenment. People with NPD carry a substantially larger amount of suffering in their unconscious than regular people, they suppress a lot more pain.

Another polar opposite would be Multiple Personality Disorder, basically two or more egos. A third one could be anti-social psychopathy.

It’s hard to point out one particular polar opposite, since spiritual enlightenment is the center, and ego is the multiple layers of illusion around it. So a center of a circle can have very many polar opposites. The thicker the layers, the greater the illusion. The further one is from the center, the greater suffering separates them from reality. Both the extremes of vanity and the extremes of self-hatred and anxiety can be considered opposites of the center, even though they are opposites of each other on the circle.

All psychiatric disorders are diseases of the mind, its imagination running amok. How far it can go is probably only limited by the brain’s capacity to imagine, and all we can do is point out examples in the psychiatric literature. So, the polar opposite of spiritual enlightenment would be those states and disorders where the imagination of the mind starts to seriously interfere with your day-to-day functioning as a living organism. Most people in the separated state manage to combine the two without much difficulty and die of the old age, just like most enlightened people do. Very few people commit mass murders, eat their babies or do otherwise horrendous things. These examples constitute a very profound loss of touch with reality, and they usually result from being subjected to extreme cruelty in childhood.