Complete Monster: Krug is the leader of a group of murderous rapists. After he and his gang escape prison for their previous crimes, they kidnap, rape, torture, and kill two teenage girls. The parents of one of the girls find out when the criminals incidentally stop at their house, leading to a bloodbath between Krug's group and the parents. Aside from leading a group of horrible rapist scum, Krug also brainwashed his own son and kept him hooked on drugs as a kid as a means to control him. Near the end of the film, he convinces said son to kill himself. So yeah, you definitely root for the vengeful dad to take Krug down with the chainsaw.
Moral Event Horizon: If you had not lost faith in Krug when he rapes and kills Mari, then you will when he convinces his son to kill himself. As the latter doesn't happen in the remake, you'll lose any interest in seeing him live when he brags about raping Mari and how much he enjoyed it to her father while beating him up.
Narm: The original has a fair amount. Hey, it's a low-budget '70s horror flick.
The bumbling comic-relief cops manage to wipe out most of the film's tension every time they step into the frame.