Just a thought, but what about a super cute creature. It would super reduce stress if allowed to live, but would eventually (several cycles) turn into a horrible monster if left for a set amount of time. Maybe not attack Duplicates, but would destroy machines and eat resources. Killing them as the cute form would make stress increase, but would be less than allowing an attack from them. "Awww it's soooooo cute, and it gives my dups so much happiness!" 5 cycles later. "WTF! WTF is THAT! WHY!!!!!!!"