Violence isn't frequent early on but becomes very present later. Many scenes are pretty graphic, intense and bloody but what makes the show's violence have a higher impact is its realism and upsetting nature. Suicide and implications of sexual violence are also depicted throughout the show. Most of the violence is very sudden, unexpected and shocking rather than gory, but there is a particularly gory and graphic scene at the end of season 3.
The violence becomes increasingly more intense as the show progresses. Almost every scene of violence in the show is unexpected and shocking.
Season 1 has a few violent scenes while seasons 2, 3 and 4 have lots of violent and bloody scenes.
In season 2, a man is about to be gang raped when he is saved by his friend who kills the men with a knife blurred in the background (we see spurting blood when their throats are slashed) and then after blood stains the walls. Then we see a man (the rapist) having a knife rammed in between his bare buttocks with blood shown.
A man is killed with an axe in brutal gory detail. Blood splashes in heavy amounts and his lifeless body and head is hacked into onscreen from a distance.
Canonically, Dark Army operatives are trained to commit suicide after carrying out their mission, and as a way to prevent capture by law enforcement agencies. Several of them are depicted shooting themselves in the head (often suddenly) with splattering and gushing blood.
The violence is infrequent but usually very shocking. Blood is often shown and many of the violent scenes are unexpected albeit not as intense as other shows visually.
Season 1 has a handful of shootings with visible blood, a graphic suicide and a few other violent scenes. The first three episodes of the show are completely clean in this regard.
Season 2 takes a large step up in violence from the first season which, while bloody, only had around 5 scenes of violence. In season 2 violent scenes occur more frequently and are more bloody.
Moderate violence in season 1 and occasional graphic violence in seasons 2-4. Shootings, beatings, stabbings and suicides included.
The violence is overall severe as the level of brutality increases with each season.
The violence in some episodes can be very brutal and jarring while the majority of episodes have mild to moderate violence.
The violence becomes much stronger in the second season and continues to be like this throughout the rest of the show.
There is a sudden and disturbing scene where a woman is shot in the head in front of her infant baby. Blood splatters all over the babies face who starts screaming and crying and a bloody bullet hole is shown in the woman's head. The next scene is a graphic sequence where her skull is chipped open in autopsy revealing her brain and folded scalp.
A graphic suicide in season 1 shows a man shoot himself in the mouth on live TV. Blood and brain splatter all over the window and then start gushing out of his mouth realistically. This is one of the most shocking and bloody scenes in a mostly non-violent season.
In the early segments of season 2 there is a sight of a throat slicing with squirting blood, multiple images of people being shot in the head and throat with splattering blood along with self harm in the form of purposeful drug overdose.
Brutal violence in all seasons but season one.
Out of all seasons, season 3 has the most graphic and disturbing violence despite the violent scenes being spread out.
Moderate violence in the first half of the series and lots of graphic violence in the second half.
Viewer discretion is advised due to their being a great number of explicit scenes of suicide by gunshot throughout the show with varying amounts of detail. Most notably graphic scenes take place in S1 E10 (the most explicit scene), S2 E5, S2 E10, S3 E10, S4 E3, S4 E4 and S4 E11.