Tom Welling and Michael Rosenbaum tackled one of the most iconic rivalries in the superhero mythos. Lex, the rich boy neglected by his father, hated farm boy Clark, who had everything: friends, family and a super secret that Lex tried to expose.

Young Claire Bennet (Hayden Panettiere) had the one power Sylar (Zachary Quinto) desperately needed — invincibility. Their rivalry intensified once Sylar killed her pops and was forced to take on his persona by Matt Parkman (Greg Grunberg).

Arvin Sloane (Ron Rifkin) was the head of SD-6, an international crime organization — though he convinced Agent Bristow (Jennifer Garner) it was a black-ops division of the CIA. For the next five seasons, he murdered, maimed and tortured just about anyone connected to Sydney because of his obsession with Rambaldi, who named Sydney his "chosen one."

After killing off survivors he deemed unworthy, the Man in Black tried to convince the remaining candidates that the island didn't need protecting. He appeared as John Locke (Terry O'Quinn), who was killed by Ben, to gain their confidence. In the end, Lost's protagonist, Jack (Matthew Fox), sacrificed his own life to kill the evil smoke monster and protect the island — and the world — from evil ... we think.

Like the Joker of legend, Batman's Joker (Cesar Romero) from the 1960s series had a twisted, malevolent sense of humor, leaving clues for Batman (Adam West) and Robin (Burt Ward) at the scene of his crimes. Along with the Penguin, Riddler and Catwoman, he goes down as one of the show’s most popular villains.

Recently introduced in the CBS remake, Wo Fat was Steve McGarrett's archnemesis in the original series. Currently on McGarrett's watchlist, Wo Fat is a criminal with ties to the Yakuza — and may be responsible for the murder of Steve's mother.

To escape suspicion of being criminal mastermind Chess, Peter Fleming (James Frain) frames Vince Faraday (David Lyons), a decorated cop. After Vince is seemingly killed, he takes on the persona of The Cape to take the real Chess down and win back his family.

The Vampire King of Mississippi tries to get Bill to blackmail Sophie-Anne into marrying the King, uniting their two territories and making an ultra-strong vampire kingdom. Russell also tries to acquire Sookie and her mysterious powers, but is thwarted by Eric, who kills Russell's lover because Russell killed his family many centuries ago.

Before turning into a blood-sucking villain, Katherine (Nina Dobrev) bore a child. More than a century later, her great-great-something turns out to be her doppelganger, Elena, who has gained the Salvatore brothers’ attention. Katherine's main concern now is handing over Elena and all of her friends to Klaus — a vampire original who wants to break the vampire curse — in hopes of gaining his forgiveness.

While trying to rescue Peter (Joshua Jackson) from the alternate universe, Olivia (Anna Torv) is kidnapped by Walternate (John Noble), while Alt-Olivia goes back to the original universe posing as the Fringe Division agent to infiltrate and stop them from destroying her universe. She also stole Olivia's man. Home wrecker.

In the BBC update of the Victorian classic, the crime-solving Sherlock Holmes (Benedict Cumberbatch) exhibits a quirky genius that is only fully understood by Moriarty (Andrew Scott), an evil mastermind who delights in strapping bombs to innocent victims, who are forced to read clues to Holmes that he must solve within a specified time to save their lives. Moriarty makes the rivalry personal when he selects his next victim: Holmes' loyal partner, Dr. Watson (Martin Freeman).

Spike (James Marsters), who had a knack for killing off slayers and enjoying it way too much, headed to Sunnydale to kill off the next in line: Buffy Summers (Sarah Michelle Gellar). Throughout seven seasons, they went from mortal enemies to bed buddies and back again, while he always tried to one-up her true love: Angel (David Boreanaz).

Nikita (Maggie Q) wasn't the first girl to be turned into an assassin by Percy (Xander Berkeley) and Amanda (Melinda Clarke), who run a secret government agency called Division, but she is hoping to be one of the last. Using the skills they taught her, Nikita — and her inside woman, Alex (Lyndsy Fonseca) — attempt to take down the organization that does more harm than good.

Among the many nemeses of Jack Bauer (Kiefer Sutherland), Charles Logan (Gregory Itzin) was one of the most slippery and dangerous. Not only was he involved with President Palmer's assassination, but he sold Sentox nerve gas, which was used in an attack on CTU, to terrorists. He was later pardoned, and used President Hassan’s assassination as an entree to clear his good name by helping the White House. When that all went to hell, he shot himself in the head.