Pifias

During the family massacre scene, one of the children is decapitated, but the "head" is clearly fake. First when it drops down from the table it looks a lot bigger and doesn't have colored eyes (they have the same skin-coloring effect). And secondly when we see the whole room, the head on the floor looks almost pale-white. It's really white actually, and that's weird because the family was "slightly dark" skinned.

When Wong Chi Hang kills the first child, you can see that the cleaver travels through the child (positioned on the right side of the scene) and the blood splatter spurts on Wongs face directly from the underside, nowhere near where the child was positioned earlier.