The Neighbor (1993)

Myron suffocated his baby brother because he blamed his offspring for causing his mother's death. Myron kills the nosy family dog, Poison's John's (the husband) boss and stabs/impales Mary(the pregnant wife)'s physician who's treating her (using some sort of a surgical tool). Mary fails to kill Myron by knocking him down some stairs, so she runs him through with a giant surgical syringe of sorts continueously till he dies.

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