If someone tasked you with choosing the form of a monster that will destroy the world, Mr Stay Puft probably isn’t the first image that would spring to mind. Sure, it’s a funny visual when he emerges through the buildings, but that’s part of what makes him so sinister.
He wears a sweet smile the whole time he's stomping buildings and watching people flee in terror, and while he’s trying to murder our heroes. While Ghostbusters is best remembered for the comedy elements, it was quite good at milking scares too - think of the opening library scene - and it combined horror and comedy perfectly with this final showdown.
Mr Stay Puft wasn’t invited back for the sequel, and become the butt of a silly sight gag in the reboot. The fact he wasn't overexposed allowed him his perfect moment in the original, which is why he's become so iconic.