A real 90 kyat bill
The President of Myanmar ruined the economy by reissuing the currency because he believed astrologers. Astrologers told him that his lucky number was 9 and he could live until 90 years old if he was surrounded by that number. Therefore, he changed the counting system from metric to the base-9 system and issued 45 and 90 kyat bills. As a result, the economy collapsed.
I think belief in astrology is the biggest problem. If someone believes in astrology and makes a decision on advice from an astrologer, we have big trouble. Depending on the person, it is going to get decided if astrology is the harm.