Oh Celestia how would I pick... I adore a lot of my characters honestly. More than I think most writers do, based on what I hear. Alunya would be the most obvious pick but, I think I'm going to have to say Saoirse Starshot? I don't know if I'd say they're my best character but, they're fun to write. A servant who is close friends with two aristocrats they were raised alongside, with an ego vastly outsizing their social status combined with a reckless nature, compensated for by the fact they are actually as talented as they believe they are. I have a thing for prideful characters, and Saoirse definitely fits that bill, but has a decent amount of depth too, along with a very complicated relationship with their two best friends, given that they hate the aristocracy but also have aristocrats as their main friends. Honestly though there's a lot I could say, I kinda adore most of my protagonists in general. I suppose I'm just as prideful as the characters I like in my own way, ha.
As far as most hated... Hrm. There's quite a few I could immediately go to because they're obviously loathsome and evil, but it feels almost too easy. Kuzir, or Tanith, or Elias Rosewine... A few wannabe rapists, or in Kuzir's case just an incredibly vulgar and chauvinistic piece of living filth. But it just feels too easy, I couldn't properly hate them because that would require seeing them as worthy of that much attention.
Oh wait what am I saying I write fanfiction it's obviously going to be Shining Armor I fucking hate Shining Armor. I hate Shining Armor so much that I routinely go by the alias of No. 01 Shining Armor Hater. Celestia but I hate Shining Armor...
That feels like cheating though since I didn't make the character, thats just in fanfiction. I'd say the one I most actively dislike that is of my own creation would have to be the unnamed parents of Torrent and Roisin, who try to sell one of their kids to pay off their gambling debts.
I dunno. It's kind of hard to actively dislike a character of mine own creation. If I made a character I actively loathe, I generally will end up killing them off. Knowing a character is mostly there just to be awful doesn't really inspire a lot of direct emotion, the emotion tends to be more focused on the more likeable characters having to deal with it. I suppose I could angle it more as 'what character do I find most unpleasant to write', but I don't really think any of my characters are particularly bad to write, just a few are standout as particularly enjoyable.
Maybe most disappointing character? As of right now that would be Glyndwr the Gryphon. I don't actively dislike them, but I have had a bit of a slow start with them, and I feel I've failed to make them particularly engaging. So that's more of a personal failing but, thats the closest I can think of. Not that I've given up on the character, mind; I still have every intention to flesh them out into a more interesting character and hopefully actually get to do something with them. Just, hasn't happened yet.