Tough one. Definitely agree with the PredAlien.
But when I saw the newborn come out of a perfectly good queen and then decides to kill her, proceeded by following a cloned Ripley as her 'mother'. I had a small moment of thinking back to Alien and Aliens and just thinking to myself, "How in the f*** did we get to this point?" As if the newborn was the antichrist being birthed before our eyes, and the Alien franchise was dead or headed for Armageddon.
It might be my bias for A:R but sorry newborn, you remain my most hated character out of both franchise's.