Joker
It's obvious that the Joker represents a severely disturbed individual, and this is hinted at several times in the film when he attempts to tell an origin story about his facial scars.
“I Believe That Whatever Doesn’t Kill You, Simply Makes You... Stranger!”
The Joker certainly had guts, especially when it came to sauntering into a secret meeting of Gotham's most dangerous mobsters, and offering a proposal. By that time, he'd stolen from each of them, while encroaching on their territory and murdering their own men.
“And I Thought MY Jokes Were Bad!”
This quote is one of the most chilling of the entire film, and takes place shortly after one of Batman's costumed vigilante admirers winds up dead. The Joker sends them a video of him tormenting the vigilante, before issuing an ultimatum and a threat to Gotham City's inhabitants.
“I'm A Man Of My Word”
While most would be horrified by the Joker's actions, he himself sees it the opposite way. Life is a game that shouldn't be taken seriously, but rather lived vicariously through the darkest parts of his own id. Only by embracing the nihilistic humor of life, can he actually enjoy living.
“Why So Serious?”
