I'm writing from first hand experience, here.
When you have had it beat into your head that you're not as good as other people, you tend to develop an inferiority complex.
You know better, you know that other people aren't really better than you. Better at some specific thing, but not better in the sense of class. You know you are good at some things. You know that there are some things you are better than many other people at.
But you've had it pounded painfully into your head that you are inherently no good. Inferior. And pain hurts. So you pretend that you are inferior.
But it doesn't settle well. So, you tend to start finding ways to assert your superiority, to counter balance.
This is where the superiority complex kicks in.
Superiority complex can be expressed in two general ways. (Often, both ways in the same person.)
One way is to start simply asserting oneself. This much is actually not inherently bad. But if it goes too far, it becomes overweening pride, which is obnoxious. but still not too bad. One might call this supremacy complex.
The other way is to start trying harder than before. This isn't bad, it's good. But then it may progress to insisting on trying harder than other people. Again, this much is not all that bad, even though some find it obnoxious. (That others confuse it with humility is also worth noting.) It is often called superman complex.
If supremacy complex goes too far, it tends to seek identity with similar people and asserting group supremacy. (Racism, nationalism, sexism, politicized religionism, etc.)
Some of my Mormon friends got dragged into this kind of thing. I managed to stay out of it, partly because I could recognize a spirit that conflicted with the tenets of service that we call core.
If a superman complex goes too far, on the other hand, it seems to avoid group identification. There is a sense of "I can go it alone." Or, at least, a sense that one should be able to go it alone. On the one hand, you're trying to help others, but on the other hand, you aren't letting others help you.
I did not avoid this one, but I am discovering that the superhuman complex also conflicts with gospel principles. Well, I've been fighting with myself over this for thirty years, actually, so I'm thinking it might have been something I brought with me from the spirit world, from before birth.
I've noticed that a lot of the conflicts we have in this world, courtroom battles, market battles, family/spousal feuds, gang/fan violence, outright wars, seem to have roots in superiority complex.