Mikey (movie, 1992)

Mikey just needs a good stable home. He's bounced from foster home to foster home his whole life. He finally lands himself with a new loving family, but their perfect little child is not what he appears to be. His previous caretakers all died of mysterious "accidents" that weren't really accidents at all. Mikey is a cold blooded killer, and it doesn't take long for him to aim his sights on his new adoptive family and anyone else who stands in his way.