Intense violence is spread throughout the movie. Many deaths are shown onscreen, and blood is not shied away from.
Atomic Skull uses his powers to drain energy from people, which causes them to turn gray and fall to ashes.
Manchester Black uses his abilities to torture a number of people, causing blood to drip from their eyes and mouth. Superman likens this to a lobotomy.
The final battle against Superman and The Elite is very brutal, with an angered Superman becoming bloodied all over, complete with a popped vein in his eye. Superman is shown almost homicidal.