def. burayi ke naash ke liye...Rama would never have killed Ravana for a personal cause like sita's haran, all the negative deeds done by him led to his death. killing Ravan was for the good of the world and not just rescuing sita though that was def. part of it :-D
btw, even in krishnavatar, krishna stopped balarama killing jarasandha for a personal cause...only when it become a necessity for the good of the world, did krishna instruct bhima to kill jarasandha.
-Asha