Of the ones listed:
I don't think Lin has enough fully established information for a final judgement yet.
Fern is an irritating dick, but frankly he's not important enough for me to actually hate. He's irritating, but that just goes with that personality. And the fact it has to be eating away at him inside just how much better the PC is than him is a positive.
Solaris I think has an interesting backstory and as a villian is fairly solid overall. No hate there.
Blake though, honestly I don't think he has any redeeming qualities. So he wins.
Of others people have mentioned. I don't mind Titania and Sapphira's willingness to kill. Its not like the Meteor's didn't bring it on themselves. To be frank, maybe if the PC and other allies hadn't let them walk off after losing a battle every single time we wouldn't have half the problems currently happening.
Victoria I can sympathize with as someone who's trying to do good, but just can't see the big picture.
Bennett is a creepy little shit who also has no redeeming qualities.
Sirius is a villain and therefore its fine to despise him. And unlike Blake he's a fairly solid threat.
I sympathize too much with Heather to dislike her.
So, Blake is the worst with Bennett following.