yeah, i hated (ok still hate) Rachel Berry for interfering with almost all my glee OTP's, and i hated Dan and Tripp (still hate him) for interfering with Serenate on gossip girl, and i wouldn't say hated but got annoyed with Chuck for interfering with Dair. :)
Some characters I dislike only when they interfere with my couples (like now that Stelena is pretty much dead, Stefan grew into quite likeable character).
Others I just don't like in general (for example Dan Humphrey or Dawson Leery, I can't stand them even when they're not a threat to my favourites).
Not that I can remember. I'm a multishipper, so if I like the character that's interfering with my ship, chances are I'll like both ships.
That said, I disliked Belle from OUAT before she dated Will, but their brief relationship may have made me dislike her more than I already did... but mostly I just hated the writers for not explaining it.
Stiles/Derek - Lydia (Okay, before I even saw the show, I heard so much about Stiles/Derek, I had always thought that they were an actual couple, I never even knew who Lydia was until I saw the show. But the writers decided they wanted Stiles to be either Straight or bi but have him with girls ie. Malia, Lydia. I just wonder if Lydia or Malia hadn't been possible if Sterek would have happened.)
Aria/Jason - Ezra (I thought that Ezria had been cute at first but then I got sick of them and annoyed because Aria hated her dad for having an affair with a student, also cheating on her mother but then turns around and has an affair with her high school teacher, knowing the consiquences. I am so, so against Teacher/Student relationships as it is. I just think if Aria had not loved Ezra or if Ezra moved to another city, then maybe Aria could have been with Jason.)
Stiles/Derek - Jennifer/Braeden (Another reason why Sterek didn't happen, Jennifer and Braeden, they both had interest in Derek. I do have to say the writer of TW sucks.)
Blair/Dan - Chuck (I thought that Chuck was so bad for her, he was a cheater and he was a manipulater, but yet, people wanted someone like him with Blair.)
Elena/Stefan - Damon (Why are people so stupid when it comes to delena? He killed Jeremy, she hated him then loved him, who dates their ex boyfriend's brother, that is just twisted. And hello delena lovers, he was obsessed with her, he stalked her and always came up with the chance to turn her against Stefan. I hate Delena. I don't like them together at all.)
Spencer/Toby - Wren/Yvonne (I can't stand Wren, he always went after her when she was at most vulnerable, come on there was the first season when Melissa, who Wren cheated on with Spencer, practically disowned Spencer, what sister does that, then there was the second season when Spencer broke up with Toby to protect him and she was crying her eyes out and Wren came on her once again, then made out with her and kept her at his apartment when she had been waiting for Melissa before that, then there was the third season when he once again came on to her when she was really distraught and depressed after finding out that Toby had been apart of the A team, yet he decided to make out with her even after she had flipped out at Mona. He was such a moron. I don't care if he's british, that doesn't make him hot stuff or a sweet guy cause from what I noticed he wasn't any of that stuff. I just really, really don't like him. And people are stupid for liking him and Spencer together as it had all started when he CHEATED on Spencer's sister.)