The absolute worst scene in the Hobbit films, to me at least, is the Legolas/Ravenhill action sequence. Even describing the sequence hurts, because you realize that PJ actually put time and effort into something so horribly bad.
It begins with Legolas jumping onto a giant bat, flying upside down and decapitating 100 orcs before killing the bat, then conveniently falling onto a tall tower. After sniping a number of orcs, he launches a sword about 500 feet and perfectly impales an orc. He then proceeds to jump from said tower, breaking his fall by lodging his sword into the brain of a disfigured troll. He then uses said sword to control said trolls movements like a joystick, causing him to crash the tower across a chasm where he proceeds to have the most ridiculous fight possible with Bolg the orc lieutenant. Physics are defied and defiled alike. Jumping up falling rocks? Money, time and energy was spent by a lot of people to make all of that dreck possible.