Joker is the Antagonist of Dark Knight he uses to kill normal people and politician. Harvey Dent was a lawyer. but the final he becomes against Bruce Wayne.
Rachel was a lawyer and she also was Bruce Wayne friend Rachel and Harvey was a couple but Bruce Wayne love her.
Joker kidnapped Harvey and his girlfriend. Joker thought Harvey Dent was the Batman and he wanted to kill Harvey.
Harvey Dent burns his face in petrol place and Rachel died in exploding petrol. Bruce wants to save both of them the Police caught him. He wants to the prison
Joker escapes the prison he exploded Bom many people died there. and wants the hospital was in Harvey Dent. Harvey said get ready to toss Heads I win tails you win and Harvey won.
Joker did the same thing in the Hospital. he exploded Bom and he kidnapped many people in a ship Harvey Dent also killed a people. He also kidnapped Commissioner Gorden's child and wife. finally, Bruce Wayne kill them both