a breaker or destroyer of images, esp. those set up for religious veneration.

a person who attacks cherished beliefs, traditional institutions, etc., as being based on error or superstition.

noun

critic , cynic , denouncer , dissenter , dissident , heretic , image-breaker , nonbeliever , non-conformist , questioner , radical , rebel , revolutionist , ruiner , sceptic , unbeliever , individualist , nonconformist , revolutionary