Beliebers and the Navy, mostly because of how delusional they are about their faves. Monsters are horrible too, but they're like my annoying young brothers and sisters whom I make fun of frequently.
I don't hate any stanbases, but I find it annoying when stans start to talk/act like their fav. Example: #clapback. It was funny when Rihanna did it, but reading it here is just annoying. Oh, and a lot of stans or Twitter are the absolute worst.