Uniqueness
Genetically, each human is unique, not even twins share 100% of their DNA. This means that theoretically, each person should act, think and feel differently. And that is the case, at least, to an extent. However, you can also see that there are clear similarities in the way that people behave, and often, these things are integral parts of their lives. The type of work they chose, their political beliefs, and their cultural taste are just some examples. Such things should fully reflect the uniqueness of the individual, but they get lost in the wisdom of the in-group thinking crowd.
Thus, given our genetic predisposition to being different from one another, the more different a person is from what is considered normal, the more unique such a person is, and as a consequence, the more honest and true to themselves. As a remark here, when I mention normal, I do not limit it to one group of normal. There are thousands of subcultures around the world, and the majority have some kind of normal definition attached to them. Think of young graduate students who take the normal path of taking a corporate job because it is what they are supposed to do, or of the typical Italian person who will outcry if you put pineapple on pizza or the radical feminist who will see every masculine act as oppression.
As mentioned, there are thousands of subgroups and subcultures, and almost every person in the world belongs to one, no matter how niche. The more niche the subculture a person is a part of, the more it might appear to the naked eye as unique. However, under close inspection, one ends up realizing that the majority of their thoughts, opinions, and actions align with those of their subculture, even if small in size. Moreover, groups are not static. They are fluid, and one person might be a part of a group during one stage of their life and then change to another at a later stage.
So the majority of people are part of subgroups. The more you inspect these subgroups, the smaller they get. And the smaller they get, the more of an impression of uniqueness you might get from its members. The way you identify truly unique people is when you cannot pin them down to any specific group. You try again and again, but you keep encountering surprising actions, opinions, thoughts, or interests that they have that do not redirect them to any of the groups you thought they might belong to. They seem to be an almost random combination of multiple subgroups, being able to navigate these with no apparent effort. And this is exactly because they do not require any effort. Because they are being true to themselves. And by being true to themselves, they become unique. Because we are all unique by default, as long as we dare to stay true to ourselves.