Ponyhead, it's clearly Ponyhead, no joke.
I can bring up problems with Star, Eclipsa, Globgor, Meteora, Glossaryck, Rhombulus, Marco's DnD buddies, the Sensei, Mina, Jeremy, Brittney, Dennis, Moon, Hekapoo and probably a couple more. Either in terms of having a questionable role in the series, straight up being badly written or me just subjectively not liking them. However, I can at least say I either see the point of them or say that I like seeing them.
Ponyhead on the other hand is pure shit. She's annoying, detestable, has very little impact on the story, is the center of some of the worst episodes and has far more appearences than she really deserves. Jar Jar Binks is a better character than her.