Combine this quote, partial transfiguration as the power Voldemort knows not (both true and foreshadowed by Dumbledore's reaction when Harry first revealed it), the previous weaponization of partial transfiguration when Harry transfigured a cross-section of the troll's brain into acid, the shaping exercises as a Chekov's Gun, and another Chekov's gun being Harry's resolution to drop the Batman "no killing" stance if the enemy killed again.

Harry wordlessly transfigures an atomic-thickness line of material from the tip of his wand through his clothes and the ground to all Death Eaters and Voldemort, let's say transfiguring their skins to acid. That would cause blood to spill in litres, a fraction of a line of silver, and probably a scream.