Same word as re-former:

adjy, advocate, agent, anarchist, champion, demagogue, disrupter, dissident, dogmatist, fighter, firebrand, fomenter, heretic, incendiary, inciter, instigator, leftist, malcontent, mover, partisan, propagandist, provocateur, pusher, rabble-rouser, radical, reactionary, rebel, reformer, revisionist, revolutionary, ringleader, sparkplug, troublemaker, wave maker, zealot