Strong, intense violence throughout the movie.
Batman brutally beats people, men and women, cops and criminals alike, throughout the movie with oftentimes bloody results.
Joker slits a mans throat with a broken ceramic mug. The cutting is not explicitly shown, but there is copious amounts of blood splatter on the wall behind the man and on the mug fragments and the man is later seen lying in a pool of blood.
Joker kills hundreds of people by having them inhale a gas that makes them laugh so they can't breathe.
A man is crushed to death by roller coaster gears. Looking up at him you see his head enter the gears and then massive amounts of blood spray out.
Joker runs throughout a carnival shooting everyone, including women and children.
Batman throws batarangs at the Joker. Two of them lodge into the Joker's shoulder while the third lodge's in his eye. This is all very bloody.
Joker and Batman fight in a hall of mirrors. They are both cut by broken glass. Joker also is seen slamming a man into mirrors, with copious amounts of blood being graphically shown as a result.
Joker shoots Batman twice.
Batman and Superman fight at the end. This fight is very brutal, but not a lot of blood and is probably the most tame fight of the movie.
People are shot with bloody results.