The battle should reshape the landscape. The audience should realize that this battle would wipe out any civilians in the area, so that the Valar's later reluctance to intervene will be more understandable.
So, giant chasms opening up when people smite the ground, the sea rushing in, volcanoes, tornadoes, hurricanes, tsunamis, earthquakes, landslides, meteors, lightning storms....all of that at once. If we thought Ossë was out of control or violent before....ain't seen nothin yet!