Vim delete starting from character to end of line

 

A global command would be a good fit

:g/-/norm nD

Explanation

:g                 : Start a Global Command (:h :g for extra help on global commands)
/-                  : Search for -
/norm nD     : Execute nD in Normal Mode where 
                           n - jumps to the match
                           D - delete to the end of the line