Does a bad review ruin the films chances?

In my opinion, it would. The majority of people are influence on reviews, whether written or heard through word of mouth.
A trailer of film is there to attract a target audience. If one was to be intruiged by the trailer and later hears that the film is underwhelming from more than one source, then they are likely to not go to watch the film. This is because we are influenced by other poeples opinions.

If one reviewer badly rates a film and a collection of others highly rate it then the audience are likely to take the majorities opinion. It works vice versa.

However, a review also requires an unbiased opinion. If the reviewer was to review a film by a director they have a negative opinion about then this would represent a bias opinion. It is the fault of the audience to research thoroughly into a specific film's reviews to make sure they recieve a full evaluation.

An example of a recent film with a bad review is Grunge Match by Nick de Semlyen from Empire Magazine. They gave the film 2 out of 5 stars (poor under their ratings).
Plot: Two old boxing pros (De Niro and Stallone), long-time rivals now in the autumn of their careers, are lured back into the ring for one final glory bout.
Review: Sylvester Stallone is the old paunchy, grumpy one and Robert De Niro is the other old, paunchy, grumpy one in this big-screen adaptation of the classic Balboa-versus-LaMotta pub debate. As a couple of washed-up stumblebums training for a rematch, they gamely send up the movies Grudge Match is inspired by (Rocky via a meat-punching joke; Raging Bull via a puppet show in a dive bar), but unfortunately, despite the dream-team pairing, this is a dreary, spark-free affair that seems to take forever to get into the ring. Alan Arkin’s dick jokes are as good as it gets.