He fakes being strong so his image looks better but inside he really just wants someone to love him. He is not as strong as he makes himself out to be, he pretends to be this badass kid when really his bark is worse than his bite. He acts like this because his whole life has been spent hiding from other trolls to keep himself alive. HE has never really known what it was like to have friends, REAL friends with no secrets(BEFORE the game that is.)
He is so scared of being killed because of his mutation that he has never really trusted anyone enough to be nice to them for fear that they will find out and he will be killed on the spot.
With the odd way Crabdad treated him, he is sour to almost everything. Even though Crabdad probably had unconditional love towards him, his crabby attitude didn’t allow that to be shown for Karkat to understand what it means.
With everybody in the world pratically telling his exsistance isn’t okay really gets to him so inside he is this broken boy that just wants to be accepted for what he is.
His role as ‘leader’ helps him to feel better about being as low as low can be.
The people that know of his blood should keep their mouths shut about it because it sets him off. He will get angry and rant and rave about how everybody secretly hates him for it and the only reason they keep him alive is because he could have provided the needed material to help bring back the troll race.
With my Karkat’s Highblood situation, if he wasn’t scared enough of sex before this, now he was traumatized of it. In his mind now he is nothing more than a toy, that is all he thinks himself worth in the eyes of adults. He will probably never have a good sexual relationship with anybody, and when I say that I mean sex with people like his matesprit. Even if he did pail with his matesprit or kismesis, he would see it as something he HAD to do not something that he willingly gave in to.
I suppose that is all really. I will add some stuff later. All of this applies to my Karkat.