Marvel Visionaries: John Romita Sr. #1

Bill and Jenny adopt a baby but it soon runs Jenny ragged. Bill finds his coffee poisoned and they both nearly die in a mysterious fire, yet the baby somehow got out of the house before the blaze erupted. After Jenny tripped on the baby's teddy and fell to her death, Bill suspected the baby was responsible. Taking Bill's gun, the baby confronts Bill and reveals its true nature: it's an alien in disguise, killing from safety thanks to its innocent appearance. The baby kills Bill and is later adopted by another couple.