The Collaborative International Dictionary of English v.0.48:

Troubler \Trou"bler\, n.
   One who troubles or disturbs; one who afflicts or molests; a
   disturber; as, a troubler of the peace.
   [1913 Webster]

         The rich troublers of the world's repose. --Waller.
   [1913 Webster]

WordNet (r) 3.0 (2006):

troubler
    n 1: someone who deliberately stirs up trouble [syn:
         troublemaker, trouble maker, troubler, mischief-
         maker, bad hat]