Nondescription
I dislike the cliched personality type of the 'brilliant sociopath' protagonist.
Even if it's only an act, even if they're able to back up their poor behavior, even if the actor/actress playing them is attractive - if they belittle everyone around them as a result of how intelligent and misunderstood they are and that's a central part of their character (i.e., they continue to be that way well past the climax), I'll feel awfully disgusted. This can ruin entire movies for me, unless the sociopath is an antagonist.
Although really, I guess it's because that personality type is usually poorly written. In a poorly-written show/movie when a hero is a sociopath, people still stay around him for some reason. They put up with his abuse basically because the writer of the story wills it, which feels like the story is bending to the character's narcissistic view.
The writer will throw in some parts that show the sociopath's softer side, to make them more 'human', but they destroy that with the hopes of keeping that audience that only watches for the hero's 'witty' observations of his secretary's lack of lipstick or his partner's involvement in a war/how they're going to be roommates/what his psychiatrist says...
THANK. YOU.
In a semi related note, and encouraged by an overdose of James Patterson books,
-Serial killers who are far too often beautiful, wealthy, impossibly smooth, special forces trained ubermensch who make fools out of EVERY level of law enforcement. Reality is, serial killers are most often creepy losers on the low end of life.
-Even blatantly sloppy killings are written off as "OMG, perfect murders!" Guh.