I've seen other MC, and most of them tend to be similar to another, including MC in harem novels. I want to know what makes the main character unique and stands out from the rest MCs if that makes sense. So, what makes the main character unique from the common tropes of MC?
What makes the Main Character unique?
You have to create something purely from your imagination. If you try to copy others you will never have a unique story and characters.
TheRavenMocker Main character isn't made unique by something. It's the Uniqueness that makes a person THE Main character!
TheRavenMocker Probably their goals, internal struggles and the way they think. The thing, that makes the MC's unique is the characterization of the character. For example, take Cid Kagenou from eminence in shadow and then another isekai mc as an example. Even though they are both probably 'overpowered Isekai MC's' Cid's personality, his goals, his dialogue and the overall way he acts completely distinguishes him from other Isekai Mc's.
Rather than focusing directly on what makes a main character unique, I think one should instead apply careful characterization to form the character. You don't want to be adding gratuitous details, simply because it makes a character unique, you want to add them because they are meaningful to the character. Basically, don't think in terms of uniqueness, as it will damage the quality of your character, instead focus on said quality and the character's place in the overarching story. There you will find the uniqueness you're looking for, not by specific characteristics of main characters, but by these characters' roles in the stories you have to tell. Just my two cents anyway.