Inferiority is (a) a belief, about (b) a property of my self that (c) is relative to other people, and (d) found wanting or lacking in comparison.
(a): Belief implies the level of knowledge. Inferiority is something you know to be true. But just because it's knowledge doesn't mean it's conscious. You may disavow that knowledge and say "I am not inferior... [but still, I believe I am]". As with any belief, the trick isn't to "replace" it with a new belief, but to undermine its grounding, to unsettle your knowledge.
(b) Inferiority is always about Me. It's a belief (knowledge) about my self. But what is "knowledge of the self"? It seems like a set of patterns that can be used for predicting your future behavior. "I am an inferior basketball player" implies "if I play basketball against most people, I will lose". So in this sense, beliefs about the self are useful. They help you avoid bad situations and know when to dive into good ones, a little bit of future-predicting magic.
But two different things can happen: (1) your self-knowledge can become dated if no longer tested, and (2) your self-knowledge can become outright wrong as your self changes. (2) without (1) is easy to fix: you simply continue testing your self-knowledge against the reality, proving the belief wrong, and eventually your belief corrects itself. But (1) is hard. How do you know whether your belief accurately predicts if you don't have a chance to test it out? This is the challenge of "unsettling your knowledge". You can only do so by producing new knowledge that conflicts with the old knowledge and forces a reconciliation. So if you have a dated belief, you need to exercise it every so often, to see if it's still true.
There is a deeper problem, though. Sometimes even conflicting knowledge fails to upend a belief. Instead, it becomes rejected, or turned into an "example that proves the rule". In this case, there is usually a deeper reason why the belief is maintained rather than rejected. And the ultimate reason for this sort of mental phenomenon is always that, on some level, you enjoy (or "need", as one might also put it) the belief. Seems paradoxical at first, for something like "inferiority", but this happens if the fact that you believe yourself to be inferior also permits you some other "gain". Like if you believe you're an inferior basketball player, then you might choose to sit out, and no longer have to face the (pure emotional) threat of losing (or even the exertion of effort required to play). As you sit in the bleachers, you may think "wow, I'm so glad I didn't have to play that. It wouldn't have been fun." And so, you've gained something from the belief.
You've also done something potentially bad, though: created a negative feedback loop. Since improvement occurs through practice, and the belief lets you avoid practice, the belief "reinforces itself", becomes stronger as a direct result of actions taken on its behalf. Even if you choose to test the belief again, it will remain true: as a result of your own actions (the refusal to practice), you've made it so. The only way to avoid this trap is to look the "gain" in the eye, and say "no, even though it will hurt, I choose to play today." If "insanity is doing the same thing over and over again, but expecting different results," then some things take a little bit of insanity to overcome.
(c): Inferiority is "a belief about the self relative to other people," hence inferiority is always context dependent. But this is a paradox: there is only one "you", but there's a multiplicity of groups available for comparison! This is where something strange shows up: it's not just a belief about yourself, but a belief about others. So who are these "others" you're comparing against? "Society"? No, there is always some concrete group of people to compare with, whether they're grade school friends or professionals on TV. This furnishes another path to overcoming "inferiority": what if you could, rather than unsettling the piece of belief about yourself, change who you're comparing against?
Hard to do. Feels degrading to take a step down like that. However, in certain situations that are less explicitly competitive, this could be the right move. Like in dating: perhaps you don't need to be as "hot" as you think you do to achieve the goal (getting a date), you're just comparing yourself to TV actors. And even in competitive games, if you keep getting demolished, sometimes it's worth stepping down to a more equal opponent until you can improve your abilities. But in both cases, the original group will remain "sticky", impossible to forget about, because that's where the "fantasy" that's "beneath" the belief originated (the fantasy of being superior, rather than inferior). It's almost as if the group itself is an inherent part of the overall belief, smuggled in through the conduit of imagination. What other beliefs might contain secret groups like this? Food for thought.
(d): The final step of feeling inferior is comparing yourself to those others. This is crucial; it's where the deepest nature of the belief shows itself. How? In the "basis for comparison", or "criterion". Consider feeling inferior at basketball. "I lose every game to them" might be one version. But what about "I lose every game to them, even though my ball handling is better, because they're so much better at free throws." So now here's a particular basis for comparison: their skill at free throws. The thought emerges "I wish I were as good as they were at free throws" and suddenly you feel inferior. Every feeling of inferiority is like this. Identifying what precisely you're comparing is the key that unlocks the mystery.
But this key can also be buried beneath easy access. It can be something you may not want to admit. Something embarrassing. And it can easily be misdirected: "my free throws are worse because I'm short." No, it's because you didn't practice them as much. And the object of the inferiority can escape one's expectations: maybe your feeling of inferiority about dating ("everyone gets more dates than I do") is rooted in proving yourself to your peers ("everyone" meaning "my friends" meaning "I want to measure up to my friends!"). Many such cases! This is why the incels want "sex". Not because they're imminently horny, but because that's their basis for comparison, that's the criterion of value, the coin they want to spend to prove themselves in comparison to other men.
Once you've connected the dots here, it's easier to see paths of action. If the comparison group make you feel inferior, you can choose to see different people, or you can reflect on activities where you're not at all inferior with those same people (i.e. select a new criterion), or reflect on the times when you actually felt supported by them, even despite your alleged "failure" (i.e. attempt to directly satisfy the underlying need). And if that group no longer even exists, like beliefs originating from peers in grade school, then you can ask yourself honestly "why do I still care about what these people from a decade ago think?" Usually there's a reason, something like "because if I wasn't still trying to prove myself to them, I would be doing pretty different stuff with the rest of my life"And if that's true, then maybe consider... doing that different stuff (of course it's not always so easy, because you still need a new desire to replace that old desire, of proving something to your past peers. But that "how do I obtain a new desire?" is an entirely separate question, to be answered somewhere else).
To sum it up: Inferiority is (a) a belief, or piece of knowledge, about (b) a property of your self, or a predictive pattern of experience, that (c) is relative to a specific group of others, embedded into the knowledge, and (d) found wanting or lacking in comparison, by some specific metric or characteristic that dominates the feeling, and that also represents the key to dismantling the entire complex.