Although there are not a ton of violent scene, the violence that is there is pretty graphic. Overall this is an extremely bleak film.
Someone is brutally killed by 4-5 head blows. The attacker is mainly shown, blood sprays everywhere and on his face and clothes. The victim is partly unconscious and half of his/her blood-covered face is seen for about 6 seconds.
A metal spike is attempted three times to be driven into someone else's head (minimal blood seen). After the attacker injures his own hand, the victim is hit on the head with a hammer offscreen. They lie with a bloodied head in a small pool of blood.
Several bloodless fights/beatings, mostly dealt by hero to villain and others (for angry interrogations or escaping). But a couple of them can be violent. There is also an extended fight with some facial blood, and a small pool of blood is briefly seen at the end of it.
A man walks around a blood-covered room where murder took place, looking unsettled.
A dead woman has a bloody neck and a small pool of blood on her head. Seen for a couple seconds.
A bathroom is shown containing the corpses of two people and an severed injured woman with some blood lying about. No details visible.
A person tries to saw through his/her binds with an edge; some blood on the hand. Several bloody crime photos are on a police desk (brief)
A dead person's head and hands are in a fish tank, the head is seen in a closeup (no blood).
Some slightly bloody hair is shown briefly. A dog is briefly killed offscreen.
Someone is unconscious with some blood on the head/face. He/she is later recovering in a hospital with a couple of minor facial bruises.
A man grabs a prostitute by her hair and is implied to hit her several times. She has a bruise near her mouth and on her cheek. Her pimp arrives later and snacks him several times.