Frequent realistic shootings, stabbings, and brutal bludgeoning with blunt objects. There are many violent fist fights.
In one scene a character is brutally attacked with a golf club in the head. The first swing is fully shown and you can briefly but clearly see brain matter as well as a large hole in his skull. After the first fatal swing the attacker continues to bludgeon the victim offscreen with blood spraying up.
In the last episode, a bomb vest is triggered while somebody is wearing it. The camera shot widens at the last second and you can very clearly see the explosion ripping the victim apart. Blood and chunks of flesh are thrown in a wide area. This is shown again later briefly on a security tape. Blood and pieces of the body are later visible in scenes that take place in the same area. This is the most brutally graphic and gory scene in the series.
In every episode there are a multitude of violent fights including fist fights, fights with swords/knives/axes, gun fights, fights with explosives, bludgeoning, etc.