I want to use the phase "ray of hope". But I'm talking of the situation when earlier it was there but not anymore. Do I say "killed the only ray of hope" or "doused the only ray of hope" or "take away the only ray of hope" or "the only ray of hope was gone/lost/killed/doused/taken away"? What is the correct verb to express loss of hope?
The normal expression is "took away the last ray of hope." You can play off that by replacing "take away" with any equivalent expression, as Robusto indicates with "extinguished."
Thus, "snuffed out," "killed," "removed," etc., all possible.
Caution - "shot down" would lead to a mixed metaphor.