The most unpopular topic on Earth is Narcissism. Here is the wikipedia definition of Narcissistic Personality Disorder:

Narcissistic personality disorder (NPD) is a personality disorder in which the individual is described as being excessively preoccupied with issues of personal adequacy, power, prestige and vanity. This condition affects one percent of the population. First formulated in 1968, it was historically called megalomania, and it is closely linked to egocentrism.