A superhero cannot exist without an evil batch of villains to protect the innocent from, and Batman is no exception. The caped crusader has battled the violent, the cruel and the insane that threaten to tear apart his beloved Gotham City for decades. These multi-layered and complex antagonists challenge Batman in physical, mental and emotional ways, and, on rare occasions, the villains are able to overcome everyone's favorite dark knight. A lot of what makes Batman stories, whether at the movies, on TV, in comic books and video games so entertaining are the terrifyingly awesome villains and their sinister schemes.

The villains become even more interesting when one delves deeper into their characterization. They represent conflicts that Batman struggles with internally, but these connections are not always explicitly stated. Take a look!

1. The Joker: Insanity

When it comes to the Joker, Batman has a difficult time keeping hold of his humanity because of how vile the clown prince of crime is. The Joker's own madness correlates to Batman's slow descent into complete insanity caused by the horrific things he's experienced during his career as Gotham's vigilante.

2. Two-Face: Identity

Is Bruce Wayne the Batman, or is the Batman Bruce Wayne? Two-Face symbolizes Batman's constant struggle to balance "two sides of the same coin," so to speak. He has to be Bruce Wayne and he has to be Batman, and each piece of his identity requires an equal amount of attention, even on the days he wishes he only had to be Batman.

3. The Scarecrow: Failure

The Scarecrow has used fear gas to torture Batman on multiple occasions. In many of these instances, Batman hallucinates nightmares of his allies dying or Gotham burning (figuratively or literally). To Batman, these nightmares becoming a reality would mean complete failure -- it happened once before, with the death of Jason Todd, the second Robin. The Scarecrow represents Batman's greatest fear of all: failure, either by failing the members of his family or the city he has sworn to protect.

4. Harley Quinn: Obsession

Dr. Harleen Quinzel was the Joker's psychiatrist at Arkham Asylum. Over the course of their sessions together, the Joker manipulated Quinzel into falling in love with him. He convinced her to help break him out the asylum and become his accomplice; she agreed and became Harley Quinn. Quinn's adamant obsession with Joker, despite how abusively he treats her, is tragically unhealthy, but Quinn isn't the only one with an unhealthy obsession. Batman's obsession is his vigilantism. He has to save the day no matter the cost, and when he doesn't, it takes a heavy toll on the hero.

5. The Red Hood: Closure

When Jason Todd decided to pursue the Joker behind Batman's back, it had fatal consequences for the second Robin. Batman never forgave himself for the death of his protege, and he never moved on from the brutal murder despite training a new Robin to join the Bat-family. When Todd reemerges as the Red Hood years later, disregarding everything Batman taught him about control and mercy, it poses a new challenge for the dark knight: putting his past behind him while working towards a future where he can reconnect with his vindicated ally.

6. Catwoman: Temptation

Catwoman is Batman's lustful, sinful and playful desires all wrapped in a bow. Miss Kyle tempts Batman to release his inhibitions and let his primal instincts take over. After all, it is what works for her -- Selina Kyle takes whatever catches Selina Kyle's eye.

7. Hugo Strange: Exposure

Dr. Hugo Strange is one of the few who have been able to deduce the connection between the Batman and billionaire playboy Bruce Wayne. Dr. Strange represents Batman's threat of exposure of his true identity, which would put not only himself but his allies in danger.

8. Poison Ivy: Control

Poison Ivy believes herself to be the very embodiment of Mother Nature, and Mother Nature cannot be controlled. Batman refuses to accept that some things are beyond his control, despite the effort he puts in to calculate every detail the smallest degree.

9. Talia al Ghul: Desire

The daughter of the demon is both an adversary and love interest of the dark knight. Batman knows that Talia is inherently evil like her father, Ra's al Ghul, but his desire to love and be loved by someone who understands how it feels to wear a mantle as heavy as his cowl often causes him to overlook the darkness that looms within her.

10. Bane: Hopelessness

Bane was the only one to ever break the Bat -- literally. In the infamous "Knightfall" story arc, Bane snaps Batman's spine, leaving him disabled and unable to continue fighting as Batman. There was chaos in Bruce's absence, especially when the question arose as to who would take his place. Bane represents the loss of all hope; Batman loses hope when he is incapable of protecting his city, when his body can physically no longer handle it.

11. Killer Croc: Ostracism

Waylon Jones aka Killer Croc was cast out of society for the unnatural appearance of his reptilian skin and his brute size, leading him to grow into a hostile, cannibalistic, bloodthirsty monster. Croc never had the luxury of a secret identity, and Croc doesn't get to take off his costume -- it's permanent. What would happen if Batman took off his cowl for the world to see? How would the world react? Would Bruce be shamed? Would Wayne Enterprises fail? Would society reject him and the Batman? Killer Croc represents the possibility of Batman being outcast from society if the public were to ever know the truth.

Obviously, these are only 11 villains out of the very many that make up Batman's rogue gallery, so this is in no way intended to be a complete list. It does, however, cover a great amount of ground in terms of the internal conflicts that Batman wrestles with. Sometimes these conflicts are addressed as a part of a story arc, and sometimes they're simply implied. Nevertheless, they're always there, and these classic villains are a reminder of that.