Every character in Sonic Prime.
Case in point: Sonic Prime does everything wrong, that it doesn't even have the right reasons to be made canon to the games.
For a character I find annoying that's NOT from Prime, I'd say Classic Sonic. Not like the actual Sonic, but the supposed "Classic" Sonic you see in Generations and Forces. (no, Superstars doesn't count, and no, I'm not calling him "SaNtIaGo" because that's more annoying than Classic Sonic himself.)
He's mostly a watered down version of what the actual Sonic is: a cool, superhuman hedgehog with a sense of action, attitude, and curiosity, who loves the world of nature, and despises oppression; and when oppression strikes to destroy nature, he'll take it all back in a blue blur.
"Classic" Sonic is not that. "Classic" Sonic was a way to market the "cuteness" of Sonic, and use it as the basis for two anniversary title games, which one succeeded, and one failed, a ton of merchandise and nothing else.
Sure, Generations has a really good potential in its story, but the dialogue, and even the personality of the characters, not to mention the gameplay for the most part, kind of makes it a little too... meta? And "Classic" Sonic, with being a silent character who is meant to look cute and quirky, with gameplay that is badly replicated in the Hedgehog Engine, feels like a stripping of Sonic's personality.
I don't mean to be such a double downer, but Sonic is Sonic, "Classic" Sonic is NOT Sonic. Sure, it's really cute, it's kind of like Sonic due to him basically being what Sonic looked like in the 90's, but the novelty really wears off on most cases.