Ethnocentrism could be considered a complex of some kind. It refers to having the feeling that your own culture or group is superior in some way. Although no culture, ethnicity, or group of people is superior to the rest, this phenomenon could also be considered normal and natural.
People usually consider their immediate group (friends, family) better than the others (which might also be part of our culture and ethnicity).
Therefore, it is natural for people to consider that they are somehow better than the others, their group, better than other groups.
Ethnocentrism is the belief that one’s own cultural group is the center of everything and that other groups are inferior or strange by comparison.
Such a belief becomes pathological when it goes to an extreme. When one wishes for other groups not to exist and is ready to (or dreams of being ready, able) to eliminate the other groups.
Yet again, ethnocentrism could lead to prejudice, stereotyping, and discrimination. It might create barriers to understanding and respecting cultural differences, leading to conflicts between groups or nations.