The Losers Slay It
In the book, after Eddie wounds It with his inhaler, Bill and Richie chase after It. It attempts to bargain with them, but they attack It, punching through the exoskeleton of its spider-like form with their fists and into its soft body beneath. Bill locates the creatures heart and crushes it in his hands, killing It.
In It Chapter Two, on Eddie's suggestion, the Losers initially attempt to lure IT into a tunnel to make it physically smaller so that they can kill it, but when they're unable to get It to leave its lair, they change tactics, realizing there is more than one way to make someone feel small. They hurl insults at It, depriving It of the fear that it feeds on, so that It gradually shrinks before their eyes. Bill reaches into Its chest and pulls out its beating heart, and together, the Losers crush it.