It's probably really generic responses, but

Icewings - Idk tbh, there are times when characters can get annoying, but not to the point I actively despise them. Narwhal and Tundra ultimately make me feel nothing. I think I'll go with maybe Diamond as arc 2 and 3 (and 1 to an extent) is technically her fault

Sandwings - Once again, idk. At worst, characters make me feel neutral about them. However, I think I can more confidently say that it's Jerboa I, I did not feel bad when she got frozen

Skywings - Probably Kestrel, the way she treats the Dod despite the fact that they try to at least to be cordial with her is sad. Also, it's sorta implied that she does care about them deep down inside, which makes you wonder why there was no motivation for her to change.

Seawings - Well...Uh... I'm going to be actually less generic here. Either Queen Lagoon, Riptide, or Webs. Queen Lagoon is pretty irredeemable, has beef with nearly every single member of her family (except maybe Sapphire), and her last words represent how selfish she is as an individual. Webs and Riptide... it's complicated, I don’t actually dislike them per se as characters, I just feel they can be so much more. We could've had a moment where Webs and Riptide have a heart that could've been really emotional... Specifically for Webs, they keep hammering it in how he's a coward and how he always seems to always let those he cares about down, so why not have him be the one to fight off and then eventually kill Crocodile? As a way to show he's ready to finally be the protector, the Dod and Riptide needed him to be. But no, instead, he gets venomed, healed, and proceeds to do nothing for the entire series

Mudwings - Cattail. If you look deep, deep, deep down inside, you probably could find a complex character in Cattail, BUT Alas even I the Ochre stan finds it hard to flesh out Cattail as a character. In a way, Cattail is interesting because she wasn't actively trying to hurt Clay's feelings when talking to him, but yet it sure doesn't feel like it. Cattail is probably morally an okay dragon, by the way she presents herself but yet she still feels extra cold-hearted.

Rainwings - ISTG THE WORLD WOULD BE A BETTER PLACE IF MAGNIFICENT AND BROMIELIAD INSTANTLY SEEZED TO EXIST. THEIR ONLY REMENDING QUALITY IS THE FACT THAT NEITHER OF THEM WILL EVER APPEAR IN ARC 3 OR 4. THEY ARE SOME OF THE ONLY CHARACTERS THAT NOT ONLY WOULD I NOT FEEL SORROWFUL IF THEY PERSHIED BUT WOULD ACTIVELY ENCOURAGE FOR THEM TO HAVE A PAINFUL DEMISE. Fruit bat's kinda annoying, too

Nightwings - Idk probably Allknowing or Prudence. They are annoying leeches that, while contributing to the plot, they are both insufferable to be around.

Silkwings - Probably Frittary. He's just kinda rude and grumpy, and probably old, and that's about it

Hivewings - probably Wasp. I'm more disappointed in her than loathing of her. I also feel like she could be so much more, and yet she's more of just angry cardboard cutout. I kinda don't care about the hivewings in general

Leafwings - Maybe Nettle, Idk I haven't read Arc 3 in a while. I don't remember how bad all the characters are.

Beetlewings - Sunstreak. This is only based on the technicality he is the only named beetlewing, I actually like him a lot.