A polemicist is a person who attacks someone else with written or spoken words. A heated debate is the perfect venue for a polemicist.
If you're a polemicist, you have very strong opinions, and you're not afraid to state them — even if they hurt other people. A polemicist might publish a fiery online essay criticizing many of her high school classmates, for example. The word comes from polemic, "a strong verbal or written attack," which has a Greek root, polemikos, "warlike, belligerent, or stirring up hostility."