...I always strive for a catchy title- I think I try too hard. And maybe that bothers you. ;)
...Anyway! To better explain my title- what are traits that you absolutely cannot STAND in a person? The kind of traits/attributes(physical, mental, whatever) that just make you want to turn or walk away. Let's try not to be unbearably insulting if it's directed at someone, too- sharing your opinion is fine, but let's steer clear of extremely offensive comments.
As for some of mine:
...I admit I'm a picky person. >.>
I have many more, of course, but- let's hear some of yours. Just little quirks that drive you up a wall- let's not shoot for anything huge like dishonesty unless it's the type of person who poses or makes up shit.
I suppose what I mean is, when you first meet a person, what kind of traits turn you off? Think petty, my dears. ❤

And for irony's sake, I am actually annoyed by all of the synonyms of "annoy": irk, pet peeve, what-have-you.
You wanna know what's horrible- I hate the phrase, too. I don't even really get it...a pet peeve. Is it like an annoyance you keep like a pet? However, being a writer- even if it's a poor...alliteration, is that the correct term for it?- I can't bring myself to just make a title like, "What bugs you most?" or something like that. :c

people who often joke about/think the holocaust/hitler is funny/cool
lol and i /hate/ it when people use backslashes to italicize words. like that ^
people who use excessive smilies and weird ass smilies like ;A; that take for EVER to figure what the hell its supposed to be.
people who agree with you on EVERYTHING.
i have a bajillion.
Hm, to add on since I have been inspired a bit-
I loathe people who take life too seriously. ...it sucks because I'm a hypocrite and I am totally not at all an exception to the bromide, "it's funny until it happens to you." ...But I switch between- why not laugh at whatever you want and- olulz, time to be respectful. I guess it works out in the end because I have friends for both times.
x))) ";)" smilies bother me in excess- and many times, it seems to be done in a rather condescending way. IE: "ugh, I keep staying up late every night when I have school." ";) Why not trying to go to bed early." Yeah, that gets irritating, however, ironically- I am guilty of it. >>
...Then again, I'm a hypocrite to some extent- which, unsurprisingly, plenty of people find more than just a little annoying.

People who use really annoying fonts such as yourself, .
How unfortunate. If I could, I'd make it bigger, but I can't...or at least, it won't show up for me. :B; But way to personalize it, hur.

I'm OCD and it kills me:
tags sticking out of peoples clothes,
Unever numbers or patterns,
DIRTY HANDS; okay I'm crazy enough to take a bottle of hand sanitizer everywhere and make sure everyone gets some.
No organization,
Fallen objects in stores; I literally go through the whole store picking up or reorganizing things that bug me; the employees just look and smile.
I can't go anywhere without things like this driving me crazy...
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No, it's the fact that you made it bold and so squished together, that it hurts my eyes just to read it, HUR. T_T
EDIT: Plus the color just makes it worse.
When a simple topic turns into people constantly trying to burn each other.
People who go to the extent of talking to strangers to avoid silence. Fucking annoys me if I don't want to talk and some idiot doesn't know when to shut their mouth.
On a related note: People who do that long, drawn out "Soooo....silence" in those situations. I could stab them. If you start the conversation with a 'so', you best continue it...why the hell do they expect me to reply if I'm just there minding my own business. If someone does that I either ignore them, or go "Did you want to say something?".
And I cannot stand people that try to get involved in that which doesn't concern them in the slightest. The type of people that report 1 day out of date car tax and the like.
And people that accept a country's law, unquestioningly, as their own moral code.

people who write odes and sonnets about their 'magnificent' friends anywhere on the internet and finish it with 'they're better than yours, you touch them i kill you' go die, stupid fucks
and those who can not get over the fact that i won't care about someone's personal tragedies unless i LIKE the person yeah, that includes death of the people close to you i see no point in wasting a second of sympathy, or any feeling whatsoever, if i don't like you