The Ultimate Bad Guy - Lord Voldemort, aka Tom Marvolo Riddle (Anagram for I am Lord Voldemort) (aka He Who Must Not Be Named or You-Know-Who)
Death Eaters
Avery (?)
Crabbe
Crouch Jr. (had soul sucked out by a dementor)
Goyle
Karkaroff (too cowardly to return)
Lestranges
Malfoy, Lucius
McNair
Nott
Pettigrew, Peter
Rookwood
Snape (former, turned spy AGAINST the Death Eaters)
Families killed by the Death Eaters / Voldemort
Bones (Susan Bones's parents)
Mckinnons
Prewetts
Individuals killed or tortured by Voldemort / the Death Eaters
Frank and Alice Longbottom (tortured to insanity by the cruciatus curse by 4 death eaters)
Lily and James Potter (killed by Voldemort in person)