With this year being the first in a decade that no "Harry Potter film" is being worked on or scheduled for release, those who are in Potter withdrawal can only sit back and reminisce (or pop in a DVD). You never realize how good something is until it's gone, and unlike the God-awful "Twilight" series of movies, the "Potter" movies were damn good. Part of what made them enjoyable was the cast of villains that were trotted out for each movie. Harry always had various nemeses to deal with in each of the eight movies, with each having a different rating on the skullduggery and danger scale.
What, you were expecting someone else to start this list? Maybe "He-Who-Must-Not-Be-Named"? No, it's Snape and not the "Dark Lord" and here's why. First of all, you never knew where Snape's true loyalties lie, unlike Snape (played so brilliantly by Alan Rickman) always left you guessing where he would come down when the inevitable final battle with Voldemort came. Not to mention the fact that he tormented Harry from the start and just happened to kill perhaps the most beloved character in the series, Dumbledore, and you have one vile creature. The fact that he ultimately redeemed himself in the end should make up for his sins, but damn, he was just too fun to hate to let it go.
Played wickedly over-the-top by Helena Bonham Carter, Lestrange was sadistic and deranged. Her sins in the "Potter" universe were numerous: She killed Harry's godfather (and her own cousin) Sirius Black as well as Tonks and, most despicably of all, everyone's favorite bat-eared house elf, Dobby. Also, she tortured Hermione as well as torturing Neville Longbottom's parents into insanity, she burned down the Weasley's family home (The Burrow), Hogwarts' Great Hall and loveable oaf Hagrid's shed. She met her maker at the hands of Mrs. Weasley, but she was one sexy madwoman and totally unforgettable.
Ah yes, gold old Voldy. The fear of wizards everywhere in the Potterverse, Voldemort wreaked havoc on just about everyone except his main target, Harry Potter. When it came to Harry it was failure after failure after failure. For such an all-powerful dark wizard, he always got beaten by a boy who had basically no threatening magical talent and wasn't all that bright, either. Sure, Ralph Fiennes looked great in the makeup with the CGI snake nose and he hissed and spat his lines with proper menace, but if you can't kill an unskilled boy-wizard who you've been plotting against for seventeen years, then that's pretty much a fail in. However, Voldemort wasn't all fail since he basically heaped death and destruction on wizards and Muggles alike, amassing quite an impressive body count along the way.
Ah Draco, the pompous little pure-blood that was Harry's Hogwarts nemesis from day one. The platinum-haired snob would bully, sneer and pose his way throughout the day, and with his posse of Slytherin House sycophants, including the dimwits Crabbe and Goyle, often did get the better of Harry on numerous occasions. However, in the end, Draco turned out to be gutless as he couldn't bring himself to kill Dumbledore, leaving Snape to do it. In the end, Malfoy changed sides as he just didn't have it in him to kill Harry and be on the side of Voldemort. It was probably because he was a coward, but hey, it's something.
In "Order of the Phoenix", this annoying plump little tyrant rose to Headmistress of Hogwarts and proceeded to totally abuse her power. She also gave the audience a reason to hate cats and the color pink. She made Harry's life a living hell and was so certain in her rightness that one could only compare her to a Nazi party apparatchik. She was so unbelievable loathsome that it's a safe bet that more than one theater full of movie-goers stood in unison and applauded her fate at the end of the fifth movie!