I dunno, many pet peeves I usually counter with "the artist is probably young, I did the exact same things when I was young" (like adding 100 shades of neon in their hair, added wings and tails and whatnot). I think it's a thing you have to go through and explore =) I probably made some really weird design choices back in the day ("he's got to have blue hair!"), but it's a part of learning =) And I'm still a sucker for tails, even though it'sprobably very impractical...but so cute!
But yeah, as @AnnaLandin mentioned, oversexualizing just because you can without any reason and out of a sexualised context is probably what pisses me off nowadays.
And of course the boob sock, which @NickRowler mentioned. Omg whyyy?