Son in the third act...spoilers

Sam's actions and refusal to give way to the babadook to save his and his mom's life really escalated the movie for me. Not only did it allow the viewer to continue to build on the intensity of the third act but it also provided the pinnacle of the movie for me when Sam had her tied up in the basement and used his words and his love for her to shatter the hate/resentment she was harboring for all those several years. Very intense stuff, all kinds of heroism there, and not to mention him kicking ass all over the house rambo style...really took the movie to another level for me overall.