There have been indeed many individual Dark wizards who have successfully mastered the arts of Black Magic and had cause all, Muggles and magical folk, to shiver every time they were mentioned in a discussion. 

Among the greatest Dark wizards is, of course, Voldemort, who had been born as a Muggle with the name Tom Marvolo Riddle, which was changed when he scrambled the words of his name into the phrase "I am Lord Voldemort." He attempted to acquire the Philosopher's Stone, also known as the Sorcerer's Stone, to become immortal and back to life once again, but have failed; he had led an innoent Gryffindor student to open the Chamber of Secrets; he was reborn and had murdered a Hufflepuff student who was warped into a graveyard with the Gryffindor Fourth Year during the final task of the recent legendary event, the Triwizard Tournament; he led Death Eaters to attacking innocent Muggles along with wizards and witches; he had ambushed Hogwarts School of Witchcraft and Wizardry, where he was defeated by Harry James Potter. He is undoubtedly one of the most notorious villains of history.

Another famous Dark wizard is Gellert Grindelwald; he was a student of Durmstrang until his expulsion for studying the Dark Arts. He later vandalized the school with his special mark. He had set out for a quest to find the Deathly Hallows with Albus Percival Wulfric Brian Dumbledore. When Dumbledore's siblings, Aberforth and Ariana Dumbledore joined the quest, Ariana later died in a minor conflict between the members by accident, which caused both of the Dumbledores to leave. Grindelwald, however, continued the quest and found the Elder Wand from the wizard Gregorovitch. He used it to later duel Dumbledore, and Grindelwald lost even with the invincible Elder Wand. He was later killed by Voldemort when he refused to tell where the Wand was in the fortress that he himself had made. 

The next Dark wizard is Herpo the Foul. Indeed, as his title tells, he was a foul evil wizard. He discovered and created the Basilisk by causing a toad to hatch a chicken egg after many experiments. As he was a Parselmouth, he controlled the Basilisk for his amusement and good. Breeding Basilisks was after that illegal since the medieval ages, though his Basilisk had survived for close to nine hundred years.