The next sequel to 2011's successful "Batman: Arkham City" was launched this week. "Batman: Arkham Knight" is the conclusion to the "Batman Arkham" series of titles, and is now available for PlayStation 4, Xbox One, and PC. 

Part of the pop culture success of the "Batman" franchise is its long list of memorable characters, especially the villains. The depth and back story of each enemy makes a "Batman" title, be it a game or film, much more striking. 

For the last installment in the "Batman Arkham" series, which of the villains stand out the most? 

The Scarecrow 

Serving as the main antagonist in "Batman: Arkham Knight," Dr. Jonathan Crane experimented with human behavior through chemicals, arriving at the villainous fear toxin. The Scarecrow first appeared in "Batman: Arkham Asylum" in 2009, and in the latest sequel, functions as the organizer for other adversaries of Batman, and holds the entire city under the threat of the fear toxin. 

Harley Quinn 

Falling in love with The Joker has made Dr. Harleen Quinzel turn from Arkham Asylum's esteemed criminal psychologist to a willing partner to most of the crimes done by her love interest. Her childish yet deadly personality is proving to be a match for Batman and his allies, and Harley Quinn continues to terrorize Gotham City in all four installments of the "Batman Arkham" series. She is also one of the two characters, the other being Red Hood, to be made available as add-on playable characters.

Arkham Knight

Not much is known about this new character created for the latest in the "Batman" game franchise, and it seems that the title "Batman: Arkham Knight" is not an ode to the main protagonist, but rather to the enemy that looks to be the polar opposite of Batman. The Arkham Knight prowls the streets fully clad in black armor and a silenced pistol.