All niceties of brotherhood and necessities of family bonds aside, Dean can't stand Sam.
Dean used to feel guilty. He's been awarded the responsibility to look after his little brother, and to do the job properly, he knows he has to give more than half a damn about him. By now, Dean only feels justified. He sees other families. He's never had the aching desire to conform to normality like Sam has, but that doesn't mean he's not allowed to borrow a dose of uniformity every now and then instead of avoiding it like the plague. He has yet to meet another brother as tolerant as he is of their siblings, and Dean knows better than anyone else that Sam is not low-maintenance. Dean knows that their manner of growing up wasn't the healthiest, nor was it the easiest to cope with, but Sam has started using it as more of an excuse instead of a pule he brings up now and then, and Dean is sick of playing therapist when he has enough analysis to do of his own mind.
He sees the brothers who don't share more physicality than a few tousles over who gets to handle the controller during a video game. He sees brothers who don't walk to school together, let alone even talk in the hallways in between classes. He sees brothers who don't spend every minute of their hour worrying about their sibling when the other isn't home before seven. He sees brothers who aren't each other's best friends, and quite honestly, he wants that more than ever wanting to not deal with lurid sights of headless vampires and werewolves bleeding to death from every orifice.
Dean ruminates over it sometimes, and can't help but wonder if that's how it would have been had his mother remained alive. When he thinks about it, him and Sam aren't amiable material. Sam and Dean gravitate to other sides of the spectrum, and were they only strangers on a street forced to be held hostage in the same cramped location for more than a few hours, he's positive that they both would ultimately be picking locks and breaking windows with their bare elbows just to get out of each other's cumbersome company.
Sam likes raisins in his cereal. Dean doesn't. Sam makes an effort to put conditioner in his hair. Dean doesn't. Sam wants to go to college and break Dean's sanity. Dean doesn't.
Perhaps it's just the way Sam has started to recoil away from it all. Dean wants to blame his teenage hormones for the irrational bipolarity starting to sprout from Sam's behavior, the way his smile is starting to be a rarity even to his brother's eyes, and the way Dean understands that it's him causing his extreme apathy recently. Perhaps it'd be easier to deal with if Dean didn't know that he was the one causing it. He's used to his father being the constant malefactor and summoner of Sam's desolation in the Winchester family, but when the fault lies on his own shoulders, he's unsure of what to do with it. He's not one for apologies, but the way Sam looks at him, as though he's waiting for an apology on Dean's part, isn't something Dean can handle every time he looks at his brother's face, contorted with discontent frowns.
Honestly, Dean hates it.
It's a build-up of things Dean despises. Sam's picked up on all of the habits that grate on Dean's nerves like a chainsaw, small and large, and seemed to grow attached to every single one of them as though they had been in his personality all along.
Sometimes, Dean wonders if Sam's always been this annoying. And then he remembers smaller Sam, innocent Sam, before he had grown a distinguishable personality for Dean to not be fond of. He recalls Sam in his youth very well, round cheeks and incoherent gurgles, fine hair always matted on his forehead and fingers furling around Dean's thumb. He had been so unspeakably delicate back then, nothing but a bundle brimming with unbridled potential. And this is what he's grown into, and Dean, quite frankly, is not impressed.
He regrets to say that he had higher hopes for Sam, and he hates that too.
Sometimes he catches Sam's glance from a few feet away, distant and silent, but still there none the less. Sam might slowly be outgrowing him concerning their height, but Dean is and always will be the older brother, and when Sam looks at him like that, he instantly loses the few years of maturity he's outdoing Sam in by scrapes and scratches. It's absolute condescension, like Dean's something Sam wants to fix, and it doesn't suit Sam's features well. There's rage embedded, straight into the curve of his lips, the poise of his forehead, the grimness of his jaw, and Sam's better off smiling. Dean would tell him just to wipe that goddamn cronyism off his features, but he knows what answer he would get as Sam's reply. That Dean deserves it. He can read faces like they're comic books, and Sam's face very clearly says it's your fault I'm screwed up like this.
And although the feeling is still skin deep, Dean is vindicated. Because for once, they're experiencing the same thing. They both expected better from each other.
And honestly, Dean hates it.
There's something satisfactory about rebelling against John, but there's also something about rebelling against Sam. Sam would be John's favorite if John was looking for a perfect son, but too bad for Sam that John wants someone as tainted as he is, someone willing to do the job, someone willing to sacrifice commonness for the better good, and Dean's proclaimed himself that position partly because he knows Sam won't. Sam doesn't approve of Dean's humanity, mostly because it's started to ebb away, which is why he's shying away from being John's perfect little solider, perfect little hunter as well.
He doesn't approve of Dean's methods of distractions, whether it's blasting music too heavy with guitar strumming to even identify the words in the Impala or turning to willing girls in short skirts and tight shirts when he has something irking him or even just not entertaining him to his par. He doesn't approve the way Dean dismisses his education and throws away his homework. He doesn't approve of the way Dean has started to realize that life is a lot easier when there is never any caring involved. Sometimes, Dean thinks that Sam doesn't approve of his brother in general, and the only reason their personalities are so polarized in the first place is because Sam is doing all in his power to turn into anything but Dean.
Dean doesn't think he's screwed up his life, but Sam does, and he hates him for it.
He doesn't think Sam is anywhere near perfect. Sam wallows in his issues like he's going to die of a brain tumor within twenty-four hours. But for the most part, Sam acts like Dean is his biggest issue.
Dean has spent every year of his life since he's first looked into Sam's half-mast eyelids as they blinked up at his big brother trying to be perfect for Sam, and he hates it. The only thing he's ever achieved is Hell, and Dean is sick of Sam's acceptance, or lack thereof.
Dean has stopped throwing away college response letters before Sam can see them. He used to, early in the morning, get the mail Sam would have requested to be delivered to their motel when they stayed in one town long enough and Sam threw out a few pretend aliases so John wouldn't be enraged by the sight of Sam blatantly applying for college scholarships, and then Dean would stuff them in his pocket until he could find a trash bin he would be certain Sam wouldn't be fishing through. By now, Dean thinks it would be better if Sam would up and leave without a word said as goodbye and head straight for a college dorm where he can live out his dream as a typical boy struggling through school without a gun slipped into his sock. He would much rather have Sam be happy elsewhere than constantly stare at his brooding face, especially when it's his fault. He's starting to grow a prosthetic heart because of all of it.
Dean doesn't consider it self-hate. In the past, he might have viewed it as pity for himself, but he can tell that it's not. He can tell when he watches Sam. When he watches his face.
Honestly, he hates everything about Sam Winchester.
He hates the way his name feels on his tongue. He hates the way his nose twitches when he lies. He hates the way he pours over a math textbook. He hates the way he remains speechless without his own vortex of thoughts when John says something particularly offensive instead of coming to Dean for mollification. He hates the way Sam leaves half of his plate unfinished. He hates the way Sam can't accept blame, or even accept reality. He hates that Sam is so willing to leave Dean in the dust with a pile of dull machetes and never-ending rolls of ammunition, one bullet for every ghost, spirit, demon, and other monsters they run after. He hates the way Sam hates him.
There isn't one single thing Dean likes about his brother. Not a single thing that he's fond of, not a single quirk that makes him smile, not a single joke that makes him laugh, not a single grin that reflects itself onto his own mouth. So when he kisses him tonight before they go to bed, it won't be soft, and it won't be forgiving. It won't even be the impassive connection of lips they've gotten used to lately, like a pair of married elders so used to the feeling of each other's arms around each other it's become routine instead of magic, but instead it'll be rough. Dean wants to use his teeth, straight where Sam's lower lip is soft against his own, rubbing, teasing, bruising until it's bright red. He wants to dig his fingernails into the small of Sam's back and taste Sam's pain, because he's positive that Sam can see his own pain without feeling it.
He almost wants it to hurt, and Dean hates it.
In all candor, all debris of their tedious past aside, all etiquette of sibling love forgotten, all promises and dedication he's sworn to his brother and father alike not considered, Dean knows he would be better off without Sam.
And he hates it.