Albus Dumbledore
Gellert Grindelwald () is a dark wizard who, on a list of "Most Dangerous Dark Wizards of All Time," would be second only to Voldemort, according to Rita Skeeter's book "The Life and Lies of Albus Dumbledore." His name is first mentioned in "Philosopher's Stone" on a Chocolate Frog card which notes that Dumbledore defeated Grindelwald in 1945.