The Army of Evil was the fighting force of Doctor Chaotica in the holoprogram The Adventures of Captain Proton. As their name suggests, they were essentially an army of evil-doers.
In 2375, photonic lifeforms mistook the Captain Proton simulation on the holodeck of the USS Voyager for reality and became embroiled in an armed conflict with Chaotica's Army of Evil. (VOY: "Bride of Chaotica!")