Habunake, definitely. One minute, it almost kills Kimori, the next minute, it ends up in what's practically a repeat of the Caterpie situation (except this time, at least something powerful like a Heracross knocked them away). The Pokemon didn't get too much redemption with Azami, considering it wasn't her final, trump card-like Pokemon, and it got offed by Donphan when it couldn't have taken out anything itself... all they needed to do was reverse the order of those rounds. Why the hell did they do things as they did? Hell, snakes in general seem shafted... Nokotchi almost never appears, and Arbok was Habunake's predecessor. Fortunately, Rocket Pokemon get at least some glorified moments, but their losses seem to greatly counter that.
Oh yeah, and Ariados. It not only gets the worst humiliation a Pokemon could suffer, but it couldn't even redeem itself by placing 1st in the appeal round of its next appearance (and it was again upped by the bas**** that beat it previously). Recently, it got set on fire and was blasted off along with 2/3 of Rocket Dan, reappearing later, burnt.
The original three Eievui evolutions, too. They got their a**es kicked by Arbok and Matadogas, only to be upstaged by their uberfied pre-evolution owned by a little boy who never battled before in his life.