I seen that single episode that she had, post Rose and I cried out loud, we lost Rose for this Ditz.
When she came back, she sorta just grew into a meh companion, not as annoying as that first ep.
Declan
For me it was Logan Echolls on Veronica Mars, hated the guy at first but he progressed enough through the show to become one of my favourites.
Declan
Donna Noble. She didn’t grab me in the Runaway Bride - but by the time she left the show, I was ready to murder the writers for what they did to her. More than any other companion, she grew and changed, and became a much better person - and then they took it all away from her. Bastards.
Keith Lemon.
The guy is very funny but such a jerk.
Saw many shows on youtube…
I even felt guilty for laughing with his jokes, because I really disliked the guy…
I had no idea that…
( no I am not going to spoil it 
)
Second Jaime Lannister, and also Sandor Clegane (the Hound). This is from the books – by the time the show came about, my opinions of the characters had already “warmed up” because I was caught up with the books.
Seven of Nine.
…I mean, okay, granted, it didn’t take very long, but I WAS still ticked off about Kes getting booted off the show!
Daisy. Daisy Adair. But I’m pretty sure it was completely intentional.
Funny, I’d say the opposite. Shawn was annoying from the start, but I put up with it due to the rest of the plot being well written, but they just ramped his annoyance factor up every year before I quit due to Shawn overload.
Yeah, Daisy was a pill, but on the rare occasions when she let her guard down, she became endearing.
Darryl Dixon on The Walking Dead. The first season and a half, he was just plain obnoxious. He had moments when he would soften a bit and I’d start thinking well he might be alright, and then he’d do something to make me dislike him again, like the scene in the barn where he called Carol a stupid bitch for caring about him.
He’s a pretty good guy now. 
PapSett - Did you see the email I sent you last week about the setters in the local shelter?
StG
Ben Wyatt in Parks and Recreation. But only because the actor who played him was such a dick to his brother (and his wife) in Stepbrothers.
I’m going to nominate Agent John Doggett from X-Files. The first time through the series, I disliked that character. I think some of that dislike was just frustration over the train wreck the series was becoming in those later seasons. After re-watching the series a few years later, I think he’s actually become my favorite character from the X-files, especially once Scully’s character has a stupid alien hybrid baby and stops being the skeptic.
Doggett is a pretty good guy and I have no problem with him or how he was played by Robert Patrick. A spinoff/sequel with him and Reyes might have been an OK show, actually.