haku was too soft as zabuza said he wasnt prepard to kill unless 1 threatened zabuza so i go with sasuke this is what saved Sasuke and Naruto if Haku was a Killing machine they both be dead then the show would end
No Haku couldn't have killed Sasuke any time he wanted to.Sadly the sharingan has become too OP for most simple Kekksi Genkai -.- morally Haku is already a better ninja, and He won the fight...could have killed Sasuke at any time.
Really wish an Ice style had been around in the series though :/